JP5564604B1 - Prediction device, prediction method, and computer program - Google Patents

Abstract

A prediction apparatus, a prediction method, and a computer program for predicting a value related to an event that changes in time series are provided.
Recording means for predicting and recording time-sequentially a value relating to an event that changes periodically and an item value of each item having each of a plurality of related events related to the event as items Means for identifying a period that has the same tendency as the temporal change tendency of the value in the most recent period of the target period, and calculating the Mahalanobis distance of each item using each item value in the period before the prediction target period Means, means for selecting a value related to the event based on the length of the Mahalanobis distance within the specified period, correlation using the selected value and an item value in a period before the period to which the value belongs And a means for calculating a predicted value related to the event in the prediction target period based on the derived correlation strength.
[Selection] Figure 10

Description

  The present invention relates to a prediction apparatus, a prediction method, and a computer program for predicting a value related to an event that changes in time series.

  Economic forecasts such as product demand forecasts and sales forecasts are extremely important in examining the direction and strategy in company management. Then, how to connect the predicted demand to the plans of each department such as sales, inventory, production, distribution, and development is a management issue. Furthermore, not only forecasts for economic events such as demand forecasts and sales forecasts, but forecasting future events using information that has changed over time is an important issue in various fields. .

  Various time-series analysis methods have been proposed as methods for predicting subsequent changes in time-series events such as the number of products demanded or the number of products sold. Examples of such an analysis method include multivariate analysis such as multiple regression analysis and T method (for example, Patent Document 1 and Non-Patent Document 1). Furthermore, various application proposals have been proposed for these analysis methods (Non-Patent Document 2, etc.).

Japanese Patent No. 3141164

Edited by Kazuo Tatebayashi, Shoichi Teshima, Ryoko Hasegawa, “Introductory MT System”, Nikka Giren Shuppansha, December 2008 Yukiya Masuda, “Research of T Method Considering Nonlinear Components”, Proceedings of 17th Quality Engineering Research Conference, p. 422-425, 2009

  The T method is not originally a method for prediction of time series data. There is no particular concept of the time axis, and it is a method for selecting which factor has the most influence on the value of an event related to a large number of factors. When the T method is used as a time series data prediction method, the relationship between the item value of each item and the signal value in a certain period is specified, and the signal value in the next period is predicted. For this reason, there has been a problem that estimation errors in the item values of the respective items overlap to deteriorate the prediction accuracy of the signal values.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a prediction device, a prediction method, and a computer program that can improve prediction accuracy by reflecting a tendency of change in a signal with time. .

  The prediction device of the present application is a recording unit that records a value related to an event that changes periodically and an item value of each item that includes each of a plurality of related events related to the event in time series. And a correlation between a value related to the event in a first period within a period recorded in the recording means and an item value related to the related event in a second period before the first period A prediction device that predicts a value related to the event in a prediction target period based on the strength of the prediction period, the same trend as a time-dependent change trend of the value related to the event in the most recent period of the prediction target period Using the item value of each item including the item value in the period before the predetermined period from the period to be predicted, and the Mahalanobis distance of each item. Means to calculate and before Based on the length of the Mahalanobis distance within the period specified by the period specifying means, a selection means for selecting a value related to the event to be used when deriving the strength of the correlation, and a value selected by the selection means , A deriving means for deriving the strength of the correlation using an item value in the period before the predetermined period before the period to which the value belongs, and the prediction target based on the strength of the correlation derived by the deriving means Prediction means for calculating a prediction value related to the event in a period.

  In the prediction device of the present application, the selection unit compares the normal probability of the Mahalanobis distance and a trend curve indicating the temporal change tendency of the normal probability, and compares the normal probability indicated by the calculated trend curve with a first threshold value. A discriminating means for discriminating between a first trend interval in which the normal probability is equal to or greater than the first threshold and a second trend interval in which the normal probability is less than the first threshold; and a period closest to the prediction target period; Section selection means for selecting each of the continuous first and second trend sections one by one, and within a period specified by the period specification means and within a corresponding period corresponding to the section selected by the section selection means Using the item value, a calculation means for calculating a Mahalanobis distance of each item and a trend curve indicating a temporal change tendency of the Mahalanobis distance, and the trend in the nearest period of the prediction target period When the Mahalanobis distance indicated by the curve is compared with a second threshold value, and the Mahalanobis distance is equal to or greater than the second threshold value (less than the second threshold value), the calculation means among the values related to the event within the corresponding period And a means for selecting a value that is greater than or equal to the second threshold value (less than the second threshold value) for both the Mahalanobis distance calculated by and the Mahalanobis distance indicated by the trend curve.

  In the prediction device of the present application, the derivation unit is configured to calculate a factor effect value indicating a correlation strength of each item with respect to a change in the value related to the event, and to calculate the event based on the calculated factor effect value. Item selection means for selecting an item to be used for prediction of such a value.

  The prediction device of the present application includes means for logarithmically converting the value related to the event, and means for performing secondary variable conversion of the item value related to the item with respect to the logarithmically converted value. The factor effect value is calculated using the value and the item value related to the item.

  The prediction method of the present application is a recording unit that records a value related to an event that changes periodically and an item value of each item that includes each of a plurality of related events related to the event in time series. And a value related to the event in a first period within a period recorded in the recording means, and an item value related to the related event in a second period before the first period. A prediction method for predicting a value related to the event in a prediction target period based on the strength of correlation with the computer, wherein the computer changes over time the value related to the event in a period nearest to the prediction target period A period that is the same tendency as the trend is identified from the period recorded in the recording unit, and the item value of each item including the item value in the corresponding period before the predetermined period is used for each item. Maharano A distance to be calculated, and based on the length of the Mahalanobis distance within the specified period, a value related to the event to be used in deriving the strength of the correlation is selected, and the selected value and the value belong to The strength of the correlation is derived using the item value in the period before the predetermined period before the period, and the predicted value related to the event in the prediction target period is calculated based on the derived correlation strength It is characterized by that.

  The computer program of the present application is a recording means for associating and recording time-sequentially a value relating to an event that changes periodically and an item value of each item having each of a plurality of related events related to the event as items. And a value related to the event in a first period within the period recorded in the recording means, and an item value related to the related event in a second period before the first period. A computer program for predicting a value related to the event in a prediction target period based on the strength of the correlation with the computer, the computer changing the value related to the event over time in a period nearest to the prediction target period A period specifying means for specifying a period having the same tendency as a tendency from a period recorded in the recording means, including item values in a corresponding period before the predetermined period before the prediction target period The means to calculate the Mahalanobis distance of each item using the item value of the item, the matter to be used when deriving the strength of the correlation based on the length of the Mahalanobis distance within the period specified by the period specifying means. Selection means for selecting a value relating to the elephant, and derivation means for deriving the strength of the correlation using the value selected by the selection means and the item value in the period before the predetermined period before the period to which the value belongs , And based on the strength of the correlation derived by the deriving means, the function is made to function as a predicting means for calculating a predicted value related to the event in the prediction target period.

  In the present application, from a recording unit that records a time series in association with a value related to an event that changes periodically and an item value of each item that includes each of a plurality of related events related to the event, The value related to the event and the item value of each item are read, and the time-dependent change tendency of the value related to the event and the item value is specified. Specify a period that has the same tendency as the time-dependent change trend in the most recent period of the forecast target period, calculate the Mahalanobis distance using the item value in the corresponding period before the forecast target period, and increase or decrease the Mahalanobis distance. Based on this, a value used for obtaining the strength of the correlation is selected. Based on the selected value and the corresponding item value, a value in the prediction target period is predicted.

  According to the present application, when predicting a value related to a periodically changing event, a characteristic time-dependent change tendency (trend) in the past signal is accurately extracted, and the extracted signal and the corresponding item of each item By using the value for prediction, a predicted value can be obtained with high accuracy for the value related to the event in the prediction target period.

It is explanatory drawing which shows the signal used by T method, and the example of the content of each item. It is explanatory drawing which shows an example of the proportionality constant (beta) and SN ratio (eta) (square ratio) of each item used by T method. It is the figure which showed the actual value of each member's actual signal value or the actual value of the standardized signal value, and the comprehensive estimated value calculated | required about each member in list format. It is a factor effect figure which shows the S / N ratio of the comprehensive estimated value of each item in T method. It is a graph which shows the influence with respect to the factor effect of each item in T method. It is explanatory drawing which illustrates a time difference model notionally. It is a graph which shows notionally the processing for determining the number of item selection. It is a graph which shows a response | compatibility with the number of item selections, and SN ratio of a comprehensive estimated value. It is a block diagram which shows the structure of the prediction apparatus which concerns on this Embodiment. It is a flowchart which shows an example of the prediction process procedure by a prediction apparatus. It is a flowchart which shows the procedure of the process performed at the time of selection of a signal period. It is explanatory drawing which shows the content of the item in a present Example. It is a graph which shows the content of the signal value used for prediction in a present Example. It is a graph which shows the sample autocorrelation function of the signal of prediction object. It is explanatory drawing explaining a signal selection procedure. It is explanatory drawing explaining a signal selection procedure. It is explanatory drawing explaining a signal selection procedure. It is a graph which shows an example of the prediction result in a present Example. It is a graph which shows the comparative example with the prediction result by the conventional T method. It is a graph which shows the other example of the prediction result in a present Example. It is a graph which shows the comparative example with the prediction result by the conventional T method. It is a graph which shows the other example of the prediction result in a present Example. It is a graph which shows the comparative example with the prediction result by the conventional T method.

The present invention will be specifically described with reference to the drawings showing the embodiments thereof.
The prediction method of the present application is based on a method using an MT system (for example, the T method) that has been used for a long time, in order to predict a change over time of a value (signal) related to a periodically changing event. A model is introduced. In the present application, item values each having a plurality of related events that may cause a signal are recorded in time series in association with the signal, and prediction is made based on the strength of correlation between the signal and the item value. One of the features is to select signals and items to be used.

  In addition, the following prediction methods are implemented by calculation means, such as a computer (prediction apparatus mentioned later) which can read each data from the recording means which has recorded the data used for prediction.

First, an outline of the T method which is the basis of the prediction method of the present application will be described. FIG. 1 is an explanatory diagram showing examples of signals used in the T method and the contents of each item. In FIG. 1, a member is an index indicating data for each unit period, and is indicated as 1, 2,..., N. The value relating to the event is recorded as a signal value M. “Item 1”, “Item 2”,..., “Item k” indicate each of a plurality of related events related to the signal value M. X ₁₁ , X ₁₂ ,..., X _1k indicate item values of each item related to the signal value M ₁ of member 1. For example, if the member has monthly electricity usage, the monthly electricity usage (W) is the signal value M, and the item values are “month”, “temperature”, “wind speed”, “precipitation ( Record the variables that would be related to the ups and downs of electricity usage, such as “monthly average”, “sunshine hours (monthly average)”, “maximum temperature (monthly average)”, “minimum temperature (monthly average)”.

  In addition, although the actual value may be used for the signal value M and each item value X, it is preferable to use them after normalization using a calculation means. In the normalization method, for example, the calculation means subtracts the average value of the item value of each item (for example, the average value of the monthly average temperature of all members to be used) from the item value X of each item (for example, the monthly average temperature). There is a way to keep it. Thereby, when the item value is plotted against the signal value (referred to as a unit space), the prediction formula can be expressed as a straight line passing through the origin.

  In the T method, a specific formula that specifies the relationship between the signal value M of each member and the related multi-variable item value is obtained, the item value of the next unit period to be predicted is predicted, and the predicted item A value is applied to a specific formula to predict. However, the item data is multivariate. For example, there may be 12 members and there are 20 items (k = 20). In such a case, it is difficult to obtain a specific expression for predicting the next signal value. In the T method, for each of a large number of items, a value indicating the strength of the factor effect with respect to signal value fluctuation is evaluated, and a value indicating the factor effect is weighted. Thereby, by selecting effective items, it is possible to perform prediction with sufficiently high accuracy by using the selected items without using data of all items.

  Therefore, in the T method, the calculation means calculates the proportionality constant β and the SN ratio η (square ratio) for each item using the members having the signal value M by applying the following formulas 1 and 2. To do. The S / N ratio is a value indicated by using the reciprocal of dispersion as shown in Equation 2, is the sensitivity of the signal value for each item, and indicates the strength of correlation between each item and the signal value.

  In addition, the above-mentioned Formula 1 and Formula 2 are formulas for obtaining the proportionality constant β and the SN ratio η (square ratio) for Item 1. The calculation means performs the same calculation as for item 1 for item 2 to item k. FIG. 2 is an explanatory diagram showing an example of the proportionality constant β and SN ratio η (square ratio) of each item used in the T method. In FIG. 2, the proportionality constant β and SN ratio η (square ratio) for each item calculated by applying Equation 1 and Equation 2 described above to each item are shown in a table format.

  Next, using the proportionality constant β and the SN ratio η (square ratio) for each item, an estimated value of the output for each item is obtained for each member by the computing means. For the i-th member, the estimated output value of item 1 can be expressed by the following equation 3. Similarly, the estimated value of the output from item 2 to item k is obtained by the calculation means.

  Thereby, the calculating means can derive the comprehensive estimation formula (Formula 4) as a prediction formula indicating the relationship between the item value and the total estimated value of the signal value. However, the comprehensive estimation formula using all items (1 to k) with respect to the signal value to be predicted does not have the highest prediction accuracy. Therefore, in order to increase the contribution to the influence on the prediction target and increase the prediction accuracy, an appropriate combination of items is selected from all items by the calculation means.

Therefore, the calculation means calculates an overall estimated value using the SN ratios η ₁ , η ₂ ,..., Η _k (square ratio), which is the estimation accuracy for the estimated value of each item, as a weighting coefficient. Therefore, the total estimated value of the i-th member can be expressed by the following Equation 4.

  FIG. 3 is a table showing the actual signal value of each member or the actual value of the standardized signal value and the total estimated value obtained for each member in a list format. Then, using the actual value and the total estimated value of each member obtained as shown in FIG. 3, the computing means calculates the SN ratio η (db) of the total estimated value for each item by the following equation 5. .

  In the T method, a method of obtaining a value called a factor effect value by using the total estimated value obtained for each item as described above, and selecting an item based on the factor effect value is used. FIG. 4 is a factor effect diagram showing the SN ratio of the overall estimated value of each item in the T method, and FIG. 5 is a graph showing the influence of each item on the factor effect in the T method.

In FIG. 4, the horizontal axis indicates items to be selected, and the vertical axis indicates the SN ratio of each item by taking the SN ratio of the comprehensive estimated value. In FIG. 4, for each item, the SN ratio of the total estimated value for each data including the data of the item, that is, the strength of the correlation with the signal value is shown on the left side, and each data excluding the data of the item is shown on the right side. The SN ratio of the comprehensive estimated value with respect to is shown. In the example shown in FIG. 4, there are 36 items, and there are 2 ³⁶ combinations of selections. The computing means derives the SN ratio of the prediction target for one or a plurality of items for each of these combinations. And a calculating means calculates the average value of SN ratio of the combination containing the said item used as object, and the average value of S / N ratio of the combination which does not contain the said item. In FIG. 4, the average value of the SN ratio including the data of the item calculated in this way is shown on the left side, and the average value of the SN ratio not including the item is shown on the right side for each item.

  In FIG. 5, the horizontal axis indicates items to be selected, and the vertical axis indicates the factor effect value, and the degree of the factor effect value for each item is indicated. The factor effect value on the vertical axis in FIG. 5 is the left side of the SN ratio on the right side (excluding items) of the SN ratio of the overall estimated value of each item indicating the strength of the correlation of the prediction target in FIG. Of the SN ratio (including items), that is, a value obtained by subtracting the right SN ratio from the left SN ratio. That is, for each item, the degree of effect on the S / N ratio when the item is included is not shown. Therefore, an item for which the calculated factor effect value is positive indicates that the SN ratio of the comprehensive estimated value is increased by using the item. In a method called a two-sided T method, only items having such a positive factor effect value are selected, and analysis by the T method as described above is performed.

  When prediction is performed using the T method (two-sided T method) as described above, the actual prediction accuracy still does not increase. Therefore, the inventor first applied the concept of a time difference model to the above-described T method, and performed conversion processing taking into account the nonlinearity between the signal value and the item value. Instead of the method of selection, a method of maximizing the SN ratio of the comprehensive estimated value is used.

Next, the time difference model introduced by the prediction method of the present application will be described.
The T method is not originally a method for prediction of time series data. There is no particular concept of the time axis, and it is a method for selecting which factor has the most influence on the value of an event related to a large number of factors. When the T method is used as it is in the prediction method, as described above, the relationship between the item value and the signal value for each item of each member is specified, and the signal value of the next member is predicted. Therefore, in order to predict the signal value of the next member, the item value for each item of the next member must be predicted. It is easily assumed that the estimation error of the item value of each item at this time overlaps and the prediction accuracy of the signal value is deteriorated. In addition, when predicting the next signal value based on time-series data, especially in fields such as economic forecasting or sales forecasting, there should be signs of future events. is there. Accordingly, the inventor decided to associate the association between the signal value and the item value for each item as described above not by the members of the same period but by the ones shifted by a predetermined time. Specifically, the computing means that implements the prediction method of the present embodiment associates the signal value after a predetermined period with the item value for each item in a certain period, and calculates Equations 1 to 5 between these values. And the signal value after a predetermined period is estimated (predicted) based on the item value for each item in the present (most recent) period using the comprehensive estimation formula obtained as a result.

FIG. 6 is an explanatory diagram conceptually illustrating the time difference model. FIG. 6 shows the passage of time from the left to the right in the figure. Each rectangle in the lower part of FIG. 6 indicates an item value of each item for each year, and each rectangle in the upper part indicates a signal for each year at the same time as each item. The time difference model, rather than associating the item value of the signal and each item in the same period, with respect to the signal M _i, item values of the items of predetermined period before _{X it 1, X it 2,} ..., X it k (In the example of FIG. 6, t = 1 year) is associated.
In the example of the time difference model shown in FIG. 6, the signal of one year is configured to correspond to the item value of the previous year. However, these periods are not limited to the periods shown in FIG. It is possible.

In the prediction method of the present embodiment, the calculation means uses the signal to which the time difference model is applied and the item value of each item as the signal value M ₁ and the item values X ₁₁ , X ₁₂ ,. The T method is applied by applying the relationship of X _1k . Then, the signal value of the prediction target period is obtained by inputting the item value of each item before the predetermined period (item values from January to December 2010 shown in FIG. 6) into the general estimation formula (Formula 4). . That is, in the time difference model in the prediction method of the present embodiment, the computing means specifies the relationship between the item values of a plurality of items and the signal values after a predetermined period, thereby determining the future signal from the past or current item value. It is possible to predict the value.

  In the present embodiment as described above, in order to predict the 2011 signal (unknown signal) that is the prediction target period, each year signal (known signal) from 2002 to 2010, and 2001 to 2009 are shown. It was set as the structure which introduces the time difference model which matches the item (known item) of each year until. Since each item of 2010 (that is, the item of the corresponding period before the prediction target period) is already acquired data, it is an item that is not used in the time difference model. This is called “unknown item”.

  In the prediction method of the present embodiment, the best prediction scheme is adopted in addition to the time difference model described above. In the best prediction scheme, items are subjected to second-order variable transformation for logarithmically transformed signals, dispersion is stabilized for both signals and items, and predicted values are selected by item selection that maximizes the total estimated S / N ratio in the T method calculation. Is the way to get.

  In the following, variable conversion performed in the best prediction scheme will be described. In the conventional T method, for each item, a straight line that passes through the zero point is set for the relationship between the item data and the signal value, and weighting based on the deviation from this straight line (numericalization as an SN ratio) is performed. In such a linear transformation, items that have less variation with respect to a straight line are items that contribute to changes in the signal value, and items that have more variation, that is, items that have no correlation between the change in the item value and the change in the signal value, This item does not contribute to the change in value. However, the item values of all items do not necessarily have a straight line, that is, a linear relationship in relation to the signal value. Therefore, in the best prediction scheme, logarithmic transformation is performed on the signal, and the item is subjected to secondary variable transformation on the logarithmically transformed signal.

  In the above-described time difference model, the unknown signal corresponding to the unknown item is unknown, so variable conversion of the unknown signal cannot be performed. For this reason, in the present embodiment, the conversion coefficient (that is, the coefficient of the secondary term, the coefficient of the primary term, and the constant) when the variable conversion is performed on the known item is used to convert the variable of the item value in the unknown item. To implement.

  Next, item selection will be described. FIG. 7 is a graph conceptually showing a process for determining the number of item selections. First, the time difference model is applied, and the signal-to-variable conversion signal value and the item value for each item are applied to calculate the SN ratio of the overall estimated value of each item by applying Equations 1 to 5. Then, as described with reference to FIGS. 4 and 5, the calculation means calculates a factor effect value for each item from the SN ratio of the comprehensive estimated value. As shown in FIG. 7, the computing means first sets the minimum value of the factor effect value for each item as an initial threshold value. The computing means selects an item whose factor effect value is equal to or greater than a threshold value, and calculates the SN ratio of the comprehensive estimated value with respect to the signal value (for example, all 1 to n). If the threshold is the initial value, all items are selected. Next, the calculation means sets a value obtained by adding a predetermined value to the threshold value as the next threshold value, similarly selects an item whose factor effect value is equal to or greater than the threshold value, and calculates the SN ratio of the comprehensive estimated value with respect to the signal value. . The calculation means repeats such processing until the threshold reaches the maximum value of the factor effect value, that is, reaches the line shown as MAX in FIG. The ratio can be calculated for each number of items. The calculation means sets the initial value of the threshold value to the maximum value MAX or more, decreases the threshold value by a predetermined value, selects an item that is a factor effect value above each threshold value, and calculates the SN ratio of the comprehensive estimated value. You may make it go.

  FIG. 8 is a graph showing the correspondence between the number of item selections and the SN ratio of the overall estimated value. In FIG. 8, the transition indicated by the black circle represents an example of the SN ratio of the overall estimated value when the logarithm conversion is performed on the signal and the item value of each item is subjected to the secondary variable conversion on the logarithmically converted signal. Yes. Among the S / N ratio values, the open square is the S / N ratio of the overall estimated value when an item is selected using the two-sided T method of selecting an item having a positive factorial effect value. Open diamonds indicate the SN ratio of the overall estimated value when all items are selected. White circles indicate the number of items with the maximum total SN ratio. As shown in FIG. 8, in the method of selecting an item having a positive factor effect value, the SN ratio of the comprehensive estimated value is not maximized. By implementing the method shown in FIG. The item with the highest value can be optimally selected.

  As described above, the present inventor applies a time difference model to the T method, calculates a signal-to-noise ratio of the overall estimated value after performing a conversion process considering the nonlinearity between the signal value and the item value of each item, The knowledge that prediction accuracy can be improved by applying the selection method of the item which maximizes the S / N ratio was obtained. Furthermore, in addition to the method such as the above-described time difference model, the inventor of the present application is suitable for prediction from the recorded signal period (members 1 to n) when selecting an item that maximizes the SN ratio of the total estimated value. The knowledge that the prediction accuracy can be improved by selecting the signal period was obtained. The signal period suitable for the prediction is selected by the calculation means based on the Mahalanobis general distance (Mahalanobis distance, hereinafter referred to as MD) related to the item value of each item. Hereinafter, a method of selecting a signal period that can improve the prediction accuracy will be specifically disclosed.

  First, the configuration of the prediction device according to the present embodiment will be described. FIG. 9 is a block diagram showing a configuration of the prediction apparatus 1 according to the present embodiment. The prediction device 1 is a computer such as a personal computer or a server computer, and includes a control unit 10, a recording unit 11, a temporary storage unit 12, an input unit 13, and an output unit 14.

  The control unit 10 includes, for example, a CPU (Central Processing Unit). The control part 10 controls the operation | movement of each part of the hardware mentioned above based on the prediction program 2 demonstrated below, and exhibits the function as the prediction apparatus 1 which concerns on this Embodiment. In addition, the control part 10 has a function as a calculating means which implements the prediction method mentioned above.

  The recording unit 11 uses a nonvolatile memory such as a ROM (Read Only Memory) or a hard disk drive. The recording unit 11 may be an external hard disk drive, an optical disk drive, or another recording device connected via a communication network. That is, the recording unit 11 is a general term for one or a plurality of information recording media accessible from the control unit 10.

  The recording unit 11 records a prediction program 2 including various procedures for realizing the prediction method of the present embodiment. A part of the recording area of the recording unit 11 is used as a database (DB) 110 that records signal values and data of a plurality of items corresponding to the values (item values of each item). The control unit 10 can read and write signal values and item values of each item with respect to the database 110. The database 110 records the signal value of each member and the item value of each item in time series, for example, in the format shown in FIG.

  In this embodiment, a value (signal value) related to a periodically changing event is a prediction target, and a value (signal value) related to such a periodically changing event is stored in the database 110 of the prediction device 1. ) And respective item values each having a plurality of related events as items, are recorded in time series.

  The temporary storage unit 12 is, for example, a nonvolatile memory such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory). The temporary storage unit 12 temporarily stores information generated by the processing of the control unit 10.

  The input unit 13 receives a user operation input using a keyboard, a mouse, or the like.

  The output unit 14 uses a display unit such as a liquid crystal monitor or a printing unit such as a printer, and outputs information processing results by the control unit 10.

  In the prediction apparatus 1 configured as described above, the control unit 10 executes a process based on the prediction program 2 to predict a signal value related to a future event. FIG. 10 is a flowchart illustrating an example of a prediction processing procedure performed by the prediction device 1.

  The control unit 10 receives input of the signal value and the item value of each item related thereto from the input unit 13, and records the received signal value and the item value for each item in the database 110 of the recording unit 11 (step S11). ). The signal values and item values for each item to be recorded in the database 110 may be input from other devices via the communication network as well as those input from the input unit 13 or other information recording media. May be input.

  The control unit 10 generates a time difference model based on the signal value recorded in the database 110 of the recording unit 11 and the item value for each item (step S12). The time difference model generated in step S12 is a model in which the item value for each item is associated with the signal value after a predetermined period of the item value of the item, as described with reference to FIG. That is, in step S12, the control unit 10 associates the signal value stored in time series with the item value for each item while shifting by a predetermined period.

  In the present embodiment, a value (signal value) related to a periodically changing event and each item value having each of a plurality of related events as items are associated and recorded in the database 110 in time series. However, a step of determining whether or not the signal value read from the database 110 periodically changes may be provided before step S12. For example, the presence or absence of periodicity can be determined by obtaining the autocorrelation coefficient distribution for the signal value and determining the presence or absence of a peak in the autocorrelation coefficient distribution. Specifically, the control unit 10 selects from the time-series signal values a sample time whose length is gradually changed from a predetermined time point (for example, the start point of the recording period). Next, the control unit 10 calculates the sample autocorrelation coefficient of the signal value for the selected sample time for each different sample time, plots the sample autocorrelation function against the length of the sample time, and there is a peak The presence or absence of periodicity is determined by determining whether or not to do so. In the present embodiment, the processing after step S12 may be executed when it is determined that there is periodicity, and the processing after step S12 may be stopped when it is determined that there is no periodicity.

  The control unit 10 performs variable conversion of the signal value and the item value for each item based on the relationship between the corresponding signal value and the item value for each item in the generated time difference model (step S13). The control part 10 performs the process which selects the signal period used for prediction using the signal value after variable conversion, and the item value for every item (step S14). Details of the process of selecting the signal period will be described with reference to the flowchart of FIG.

  Based on the signal value in the signal period selected in step S14 and the item value of each item corresponding to the time difference model, the control unit 10 uses the above-described equation 1 and equation 2 to calculate the proportional constant β for each item. And SN ratio (eta) (square ratio) is calculated (step S15).

  The control unit 10 calculates the estimated value of the output by Expression 3 for each member in the selected signal period using the proportional constant β and the SN ratio η (square ratio) for each item using Expression 3. Step S16).

  The control unit 10 calculates an overall estimated value using the SN ratio (square ratio), which is the estimation accuracy of the estimated value, as a weighting coefficient by using Equation 4 (step S17).

  Next, based on Expression 5, the control unit 10 calculates the SN ratio (db) of the comprehensive estimated value of each item based on the signal value and the comprehensive estimated value (step S18).

  The control unit 10 derives a factor effect value for each item (step S19). As described above, the factor effect value is the SN ratio of the overall estimated value with respect to the item value of each item including the item with respect to the SN ratio of the overall estimated value with respect to the item value of each item excluding the item. Calculated by obtaining the difference. The S / N ratio of the comprehensive estimated value is the strength of correlation of the item value of the item with respect to the signal value, and is a value expressed as a logarithm of a value proportional to the reciprocal of the variance.

  Next, the control unit 10 calculates, for each item number, the SN ratio of the comprehensive estimated value with respect to the item values of a plurality of items selected in descending order of the factor effect value (step S20). Details of the processing in step S20 have been described above with reference to FIG.

  The control unit 10 determines the number of items that maximizes the SN ratio based on the SN ratio of the comprehensive estimated value for each number of items (step S21).

  The controller 10 selects as many items as the number of items determined in step S21 (step S22). Then, the control unit 10 selects the item value among the item values for each item before the predetermined period associated with the prediction target period in the time difference model, that is, the item value for each item in the corresponding period closest to the prediction target period. Is applied to Equation 4 to calculate a predicted value (step S23). Β and η in Equation 4 are those calculated in step S15 (calculated from data after time difference model, variable conversion, and signal period selection). In step S23, the predicted value is output from the output unit 14 or recorded in the recording unit 11. If the signal value is normalized, it can be obtained by performing inverse transformation.

  FIG. 11 is a flowchart showing a procedure of processing executed when a signal period is selected. The control unit 10 calculates a signal trend using the signal value after logarithmic conversion (step S141). The signal trend can be calculated using a known method such as a calculation method using a second-order trend component based on a state space model.

  Next, the control unit 10 selects the same signal section as the latest signal trend in the prediction target period (step S142). Here, the control unit 10 refers to the latest signal trend of the prediction target period, and if the latest signal trend of the prediction target period is an increasing trend, the control unit 10 selects an increasing trend section in the past period, and the prediction target period If the most recent signal trend is a decreasing trend, a decreasing trend section is selected in the past period.

  Next, the control unit 10 calculates the MD (item MD) of the item including the unknown item (step S143), and calculates the normal probability of the calculated item MD and its trend (step S144).

  Next, the control unit 10 selects a signal interval for one cycle including the item MD closest to the prediction target interval based on the calculated normal probability of the item MD and its trend (step S145). The normal probability of the item MD takes a numerical value between 0 and 1. Therefore, the threshold is set to 0.5, and a first trend interval where the normal probability is a value of 0.5 or more and a second trend interval less than 0.5 are discriminated. And when selecting the signal section for 1 circulation containing the item MD nearest to the prediction target section, if the latest section is the first trend section, the first trend section and the previous second trend section Is selected, a signal section for one cycle is selected. Further, if the latest section is the second trend section, the signal section for one cycle is selected by selecting the second trend section and the previous first trend section.

  Next, the control unit 10 recalculates the item MD including the unknown item and the trend of the item MD in the selected signal section (step S146). Then, the control unit 10 selects a trend section having the same sign as the unknown MD trend and a known signal having an individual MD having the same sign as the unknown MD trend (step S147). That is, the MD (unknown MD trend) indicated by the trend curve in the most recent prediction target period is compared with a threshold (for example, 1.0), and if the unknown MD trend is equal to or greater than the threshold, the trend interval equal to or greater than the threshold and individual If the signal value of the MD is equal to or greater than the threshold value and the unknown MD trend is less than the threshold value, the trend interval less than the threshold value and the signal value of the individual MD less than the threshold value are selected. As the threshold value to be compared here, for example, a value of 1.0 which is an average value of all MDs can be used.

  Next, a specific embodiment to which the prediction method by the prediction device 1 is applied will be described. FIG. 12 is an explanatory diagram showing the contents of items in this embodiment. The items shown in FIG. 12 are items representing sales results (units) by class, and are recorded as monthly data. For example, “0-1” represents the sales performance (number) of construction machines having a vehicle body weight of 0 ton or more and less than 1 ton. In this embodiment, “6-8” (that is, a sales result of a construction machine having a vehicle body weight of 6 tons or more and less than 8 tons) is selected as a prediction target signal, and prediction is performed based on the other 17 series items. It was set as the structure which estimates the signal of object.

  FIG. 13 is a graph showing the contents of signal values used for prediction in this embodiment. The horizontal axis of FIG. 13 indicates the year and month in time series, and the vertical axis indicates the sales results (signal values) of construction machines having a vehicle body weight of 6 tons or more and less than 8 tons. The sales performance is monthly data, and in the example shown in FIG. 13, 120 (10 × 12) signal values are plotted between January 2001 and December 2010. When sales results (units) from January 2011 to December 2011 are targeted for prediction, for example, signal values from January 2002 to December 2010 and 2001 before a predetermined period (one year) from the signal time. The time difference model is generated by associating the item values of each item from January to December 2009, and the sales performance (units) from January to December 2011 is predicted.

  When the time transition of the signal value has periodicity, the processing after step S13 in the flowchart of FIG. 10 is performed. With respect to the time-series data of sales results shown in FIG. 13, the result of obtaining the autocorrelation coefficient distribution and plotting the sample autocorrelation function against the sample time is shown below.

FIG. 14 is a graph showing a sample autocorrelation function of a signal to be predicted. The horizontal axis of FIG. 14 indicates the sample time, and the vertical axis indicates the sample autocorrelation coefficient. It can be seen that the sample autocorrelation coefficient has a peak with respect to the sample time, and the sample time “12” is one period. In this case, it can be determined that there is periodicity.
In addition, the structure which judges the presence or absence of the periodicity as mentioned above may be provided in the prediction device 1. The presence or absence of the periodicity is judged outside the prediction device 1 and the periodicity exists outside. The configuration may be such that the determined time-series data is taken into the prediction device 1.

  The prediction device 1 generates a time difference model, performs variable conversion, and then executes a step of selecting a signal period. 15 to 17 are explanatory diagrams for explaining a signal selection procedure. FIG. 15A is a graph showing the time transition of the signal value. The horizontal axis indicates the year and month to which the signal value corresponds, and the vertical axis indicates the signal value (sales record) after logarithmic conversion. In this embodiment, the same signal section as the latest signal trend in the prediction target period (January to December 2011) is selected. In the example shown in FIG. 15 (a), since the latest signal trend in the prediction target period is an increasing trend, the signal interval (June 2007 to September 2009) that is decreasing is excluded from the past signal interval. , An increasing trend signal section (period other than June 2007 to September 2009) is selected. FIG. 15A is a graph showing a signal after selection.

  Next, the item MD of the item including the unknown item is calculated using the signal of the selected signal section and the item value of the corresponding item. FIG. 15B is a graph showing the time transition of the item MD. In FIG. 15B, a circle indicates the value of the calculated item MD, and a curve with a solid line indicates the trend (trend curve) of the item MD. The trend can be calculated using a known method such as a calculation method using a second-order trend component based on a state space model.

  Next, the calculated MD normal probability and its trend are obtained, and the normal probability indicated by the trend is compared with a threshold (for example, 0.5). FIG. 15C is a graph showing the temporal transition of the normal probability of the item MD. In FIG. 15C, a circle on the broken line indicates the calculated normal probability value, and a solid curve indicates the trend. The control unit 10 determines a section (first trend section) in which the trend of normal probability is greater than or equal to a threshold value and a section (second trend section) in which the trend is less than the threshold value. The symbol (+) shown in FIG. 15C indicates the determined first trend interval, and the symbol (−) indicates the determined second trend interval.

  Next, the signal section for one circulation of the item MD including the latest unknown item MD is selected. In the example shown in FIG. 15C, since the most recent signal section is the second trend section, by selecting this second trend section and the previous first trend section, a signal for one cycle is obtained. Select a section.

  Next, in the selected signal section, the item MD including the unknown item and the trend (trend curve) of the item MD are recalculated, the trend section having the same sign as the unknown MD trend, and the individual MD has the same sign as the unknown MD trend Select a known signal. 16 (a) to 16 (c) show sales results (logarithmic value) before signal selection, item MD after recalculation, and item MD including unknown item MD, respectively. (C) represents items MD including sales results (logarithmic values) after signal selection, item MD after recalculation, and unknown item MD. When the threshold is an average value of all items MD (= 1.0), as shown in FIG. 16C, the Mahalanobis distance (unknown MD trend) indicated by the trend curve in the latest period of the prediction target period including the unknown item MD. Is less than the threshold. For this reason, in this embodiment, as shown in FIG. 17C, a trend interval less than a threshold value and a signal value for which an individual MD is less than the threshold value are selected.

  Based on the signal value in the selected period and the item value for each item (after applying the time difference model), the control unit 10 obtains the SN ratio of the comprehensive estimated value for each item using the two-sided T method, and the SN ratio is maximum. A process of selecting the number of items is performed. And the control part 10 selects the item of the number of selected items, and calculates a predicted value based on the data of the selected item in a corresponding period (January to December 2011).

  FIG. 18 is a graph showing an example of a prediction result in this embodiment. The graph shown in FIG. 18 is a prediction based on the signal value and the item value for each item selected by the control unit 10 by performing the processing procedure shown in the flowcharts of FIGS. 10 and 11. The horizontal axis in FIG. 18 indicates the year and month to which the signal value and the item value for each item correspond, and the vertical axis indicates the sales performance. Values indicated by black circles from January 2007 to December 2010 indicate actual values. Moreover, the curve by the continuous line shown in FIG. 18 has shown the signal trend (trend curve) by all the signals. Each value indicated by a white diamond in FIG. 18 is a value predicted by the control unit 10 based on data in the selected signal period.

  On the other hand, values indicated by black circles from January 2011 to December 2011 indicate actual sales results obtained thereafter. As shown in FIG. 18, each predicted value can predict the average tendency of the actual value with sufficient accuracy, and the reproducibility of the actual value is relatively high.

  FIG. 19 is a graph showing a comparative example with the prediction result by the conventional T method. In the graph shown in FIG. 19, in addition to the prediction result in the present embodiment, the prediction result by the T method is superimposed. In FIG. 19, values indicated by white circles from January 2011 to December 2011 are values predicted by the control unit 10 based on data in the selected signal period, and are indicated by white diamonds. Each value indicates a value of a prediction result by the T method. The result by the T method indicates that the actual measurement value and the prediction value are greatly deviated, and the overall tendency in the prediction target period is not sufficiently predicted.

  In addition, when average absolute percent error (MAPE) is introduced as an accuracy evaluation of the predicted value, MAPE = 62.3% in the conventional T method, whereas in this application, MAPE = 22.3%. It can be seen that the prediction accuracy is greatly improved.

  FIG. 20 is a graph showing another example of the prediction result in the present embodiment, and FIG. 21 is a graph showing a comparative example with the prediction result by the conventional T method. In the example shown in FIGS. 20 and 21, the signal to be predicted is selected as “2-3” from the items shown in FIG. 12 (that is, the sales results of construction machines having a body weight of 2 to 3 tons). And the result of having predicted the signal for prediction based on the other 17 series items is shown.

  The graph shown in FIG. 20 is a prediction made based on the signal value of the period selected by the control unit 10 by performing the processing procedure shown in the flowcharts of FIGS. 10 and 11 and the item value for each item. The horizontal axis in FIG. 20 indicates the year and month to which the signal value and the item value for each item correspond, and the vertical axis indicates the sales record. Values indicated by black circles from January 2007 to December 2010 indicate actual values. Moreover, the curve by the continuous line shown in FIG. 20 has shown the signal trend (trend curve) by all the signals. Each value indicated by a white square in FIG. 20 is a value predicted by the control unit 10 based on the data in the selected signal period.

  On the other hand, values indicated by black circles from January 2011 to December 2011 indicate actual sales results obtained thereafter. As shown in FIG. 20, it can be seen that each predicted value can predict an average tendency of the actual value with sufficient accuracy although it is different from the actual value when viewed monthly.

In the graph shown in FIG. 21, in addition to the prediction result in the present embodiment, the prediction result by the T method is shown in an overlapping manner. In FIG. 21, values indicated by white squares from January 2011 to December 2011 are values predicted by the control unit 10 based on data in the selected signal period, and are indicated by white diamonds. Each value indicated indicates a value of a prediction result by the T method. The predicted value by the T method is greatly deviated from the actually measured value, and it can be seen that the overall tendency in the prediction target period cannot be predicted at all.
In the conventional T method, MAPE = 136.2%, whereas in the present application, MAPE = 21.8%, which indicates that the prediction accuracy is greatly improved.

  FIG. 22 is a graph showing another example of the prediction result in this embodiment, and FIG. 23 is a graph showing an example of comparison with the prediction result by the conventional T method. In the example shown in FIGS. 22 and 23, the signal to be predicted is selected as “3-4” (that is, the sales performance of construction machines having a vehicle body weight of 3 to 4 tons) among the items shown in FIG. And the result of having predicted the signal for prediction based on the other 17 series items is shown.

  The graph shown in FIG. 22 is a prediction made based on the signal value and the item value for each item selected during the processing procedure shown in the flowcharts of FIGS. 10 and 11 by the control unit 10. The horizontal axis in FIG. 22 indicates the year and month to which the signal value and the item value for each item correspond, and the vertical axis indicates the sales performance. Values indicated by black circles from January 2007 to December 2010 indicate actual values. Moreover, the curve by the solid line shown in FIG. 22 has shown the signal trend (trend curve) by all the signals. Each value indicated by a white square in FIG. 22 is a value predicted by the control unit 10 based on the data in the selected signal period.

  On the other hand, values indicated by black circles from January 2011 to December 2011 indicate actual sales results obtained thereafter. As shown in FIG. 22, it can be seen that each predicted value predicts the average tendency of the actual value with sufficient accuracy, although it is different from the actual value when viewed monthly.

In the graph shown in FIG. 23, the prediction result by the T method is shown in addition to the prediction result in the present embodiment. In FIG. 23, white squares from January 2011 to December 2011 are values predicted by the control unit 10 based on the data in the selected signal period, and are indicated by white diamonds. Each value indicated indicates a value of a prediction result by the T method. The predicted value by the T method is greatly deviated from the actually measured value, and it can be seen that the overall tendency in the prediction target period is also deviated from the actual value.
In the conventional T method, MAPE = 83.0%, whereas in this application, MAPE = 13.1%, which indicates that the prediction accuracy is greatly improved.

  As described above, in the present embodiment, when periodicity is seen in the time transition in the prediction target signal, the characteristic time-dependent change tendency (trend) in the past signal is accurately extracted, and the extracted signal And by using the item value of each corresponding item for prediction, it is possible to construct a prediction system that is accurate with respect to signal prediction in the prediction target period.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. In addition, the technical features described in each embodiment can be combined with each other.

DESCRIPTION OF SYMBOLS 1 Prediction apparatus 2 Prediction program 10 Control part 11 Recording part 12 Temporary storage part 13 Input part 14 Output part 110 Database

Claims (6)

A recording unit that records a value related to an event that changes periodically and an item value of each item that includes each of a plurality of related events related to the event in a time-series manner; Based on the strength of the correlation between the value related to the event in the first period within the period recorded in the item value and the item value related to the related event in the second period before the first period, A prediction device for predicting a value related to the event in a prediction target period,
A period specifying means for specifying a period that is the same tendency as a time-dependent change trend of the value related to the event in the most recent period of the prediction target period from the period recorded in the recording means;
Means for calculating the Mahalanobis distance of each item using the item value of each item including the item value in the period before the predetermined period from the prediction target period;
Selection means for selecting a value relating to the event to be used in deriving the strength of the correlation based on the length of the Mahalanobis distance within the period specified by the period specifying means;
Derivation means for deriving the strength of the correlation using the value selected by the selection means and the item value in the period before the predetermined period before the period to which the value belongs;
A prediction device comprising: a prediction unit that calculates a predicted value related to the event in the prediction target period based on the strength of the correlation derived by the deriving unit. The selection means includes
Means for calculating a normal probability of the Mahalanobis distance and a trend curve indicating a temporal change tendency of the normal probability;
The normal probability indicated by the calculated trend curve is compared with a first threshold value, and a first trend interval in which the normal probability is equal to or higher than the first threshold value and a second trend interval in which the normal probability is less than the first threshold value are determined. Discrimination means;
Section selection means for selecting the successive first and second trend sections one by one, including the period nearest to the prediction target period,
Trend indicating the Mahalanobis distance of each item and the time-dependent change trend of the Mahalanobis distance using the item value within the corresponding period corresponding to the section selected by the section selecting means within the period specified by the period specifying means A calculating means for calculating a curve;
When the Mahalanobis distance indicated by the trend curve in the immediate vicinity of the prediction target period is compared with a second threshold, and the Mahalanobis distance is greater than or equal to the second threshold (less than the second threshold), the event within the corresponding period And a means for selecting both the Mahalanobis distance calculated by the calculating means and the Mahalanobis distance indicated by the trend curve that are greater than or equal to the second threshold value (less than the second threshold value). The prediction device according to claim 1. The derivation means includes
Means for calculating a factor effect value indicating the strength of correlation of each item with respect to a change in value related to the event;
The prediction apparatus according to claim 1, further comprising: an item selection unit that selects an item to be used for predicting a value related to the event based on the calculated factor effect value. Means for logarithmically converting the value related to the event;
Means for secondary variable conversion of the item value related to the item with respect to the logarithmically converted value,
The prediction apparatus according to claim 3, wherein the factor effect value is calculated using a value related to the event after conversion and an item value related to the item. By means of a computer comprising a recording means for recording in a time-sequential manner a value relating to a periodically changing event and an item value of each item having each of a plurality of related events related to the event as items, The strength of the correlation between the value related to the event in the first period within the period recorded in the recording means and the item value related to the related event in the second period before the first period. Is a prediction method for predicting a value related to the event in the prediction target period,
The computer
From the period recorded in the recording means, a period that is the same tendency as the time-dependent change trend of the value related to the event in the most recent period of the prediction target period,
Using the item value of each item including the item value in the corresponding period before the predetermined period from the prediction target period, calculate the Mahalanobis distance of each item,
Based on the length of the Mahalanobis distance within the specified period, select a value related to the event to be used when deriving the strength of the correlation,
Deriving the strength of the correlation using the selected value and the item value in the period before the predetermined period before the period to which the value belongs,
A prediction method, comprising: calculating a prediction value related to the event in the prediction target period based on the strength of the derived correlation. A computer having a recording unit that records a time series in association with a value relating to a periodically changing event and an item value of each item including each of a plurality of related events related to the event, The strength of the correlation between the value related to the event in the first period within the period recorded in the recording means and the item value related to the related event in the second period before the first period. A computer program for predicting a value related to the event in the prediction target period,
The computer,
A period specifying means for specifying a period that is the same tendency as a time-dependent change trend of the value related to the event in the most recent period of the prediction target period from the period recorded in the recording means;
Means for calculating a Mahalanobis distance of each item using an item value of each item including an item value in a corresponding period before the predetermined period from the prediction target period;
Selection means for selecting a value relating to the event to be used when deriving the strength of the correlation based on the length of the Mahalanobis distance within the period specified by the period specifying means;
Deriving means for deriving the strength of the correlation using the value selected by the selecting means and the item value in the period before the predetermined period before the period to which the value belongs, and the correlation value derived by the deriving means A computer program for causing a computer to function as a prediction unit that calculates a predicted value related to the event in the prediction target period based on strength.

Images