JPH04235658A - Compact electronic computer with graph display function - Google Patents

Abstract

PURPOSE:To trace the graphs With relation secured between graphs for a compact electronic computer with a graph display function which contains a dot matrix type display means especially in a state where both orthogonal and polar coordinate graphs are displayed together on the same screen. CONSTITUTION:The graphs obtained from an orthogonal coordinete system function formula 13a and a polar coordinate system function formula 13b stored in a formula memory 13 are plotted in coordinates to a graph display buffer 16b from an arithmetic part 15 based on the parameters 'X' and 'theta' set in a data memory 14. Then both graphs are displayed together on a display part 17. Under such conditions, the locus of one of both graphs is successively traced and displayed with operation of a ' ' key 12h after operation of a 'trace' key 12g. At the same time, the parameter of the function of the other graph is calculated based on the present trace point with operation of a ' ' key 12i. Then a new trace point is designated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small electronic calculator with a graph display function.

0002

2. Description of the Related Art Conventionally, compact electronic calculators equipped with a graph display function have been put into practical use that can individually display rectangular coordinate graphs, polar coordinate graphs, parameter graphs, and the like.

[0003] Furthermore, some small electronic calculators equipped with such a graph display function have a graph trace function that sequentially blinks and moves the locus of the displayed graph and displays the coordinate data of each of the loci of the displayed graph. .

0004

[Problems to be Solved by the Invention] However, although the above-mentioned conventional small electronic calculators equipped with graph display functions can individually display different types of graphs such as rectangular coordinate system and polar coordinate system, Different types of graphs, especially rectangular coordinate graphs and polar coordinate graphs, cannot be displayed together on the same screen.

Furthermore, even if the above-mentioned orthogonal coordinate graph and polar coordinate graph can be displayed together, the coordinate determination parameters of the orthogonal coordinate graph are (X, Y), and the coordinate determination parameters of the polar coordinate graph are (r, θ) and their Since there is no correlation in the coordinate positional relationship, graph tracing that associates one graph with the other graph cannot be performed, and there is a problem that it is difficult to analyze their intersections, contact points, etc.

The present invention has been made in view of the above-mentioned problems, and in particular, when a rectangular coordinate graph and a polar coordinate graph are displayed together on the same screen, it is possible to associate each graph and trace the graph. The purpose of this invention is to provide a small electronic calculator with graph display function.

[0007]

[Means for Solving the Problems] That is, a small electronic calculator with a graph display function according to the present invention has a dot matrix type display section, and displays inputted function formulas in a graph form. It has a function of tracing a graph locus, and includes a function formula input means for inputting a function formula of a rectangular coordinate system and a function formula of a polar coordinate system, and a function formula of a rectangular coordinate system inputted by this function formula input means and a function formula of a polar coordinate system. a graph display means for displaying a mixture of graphs corresponding to the functional expressions on the display section; and a tracing means for tracing one of the orthogonal coordinate system graph and the polar coordinate system graph displayed by the graph display means. , trace switching means for switching the graph to be traced by the tracing means to another graph;

[0008] When the graph to be traced is switched from one graph to the other graph by this trace switching means, an adjustment is made in which one parameter of the coordinate system corresponding to the other graph is calculated based on the trace point of the one graph. Coordinate system parameter calculation means,

[0009] A trace point specifying means for specifying a new trace point by substituting the value of the parameter obtained by the different coordinate system parameter calculation means into the function equation of the other graph coordinate system. be.

0010

[Operation] That is, when tracing a rectangular coordinate graph, if the trace graph is switched, the position indicated by the coordinate parameters (X, Y) is converted to the angle θ with respect to the coordinate origin, and the polar coordinate parameter (r , θ), find the trace point of the polar coordinate graph, and
When tracing this polar coordinate graph, if the trace graph is switched, the trace point of the rectangular coordinate graph is determined based on the X coordinate corresponding to that trace point, and the trace points are related to each other. You can switch graphs.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an electronic circuit of a small electronic calculator with a graph display function.
12 is a control unit, and 12 is a key input unit. The control unit 11 controls the operation of each part of the circuit in response to a key input operation signal from the key input unit 12.

In addition to the key input section 12, the control section 11 includes a formula memory 13, a data memory 14, an arithmetic section 15, text and graph display buffers 16a and 16b, and
Display unit 17 is connected.

The key input section 12 includes numerical/character keys 12a, function keys 12b, "Y=" key 12c, and "r=" key.
” key 12d, “range” key 12e, “graph” key 12f, “trace” key 12g, “→” key 12h,
A "↓" key 12i is provided. Numerical/letter key 1 above
2a and the function key 12b are operated when inputting a functional formula for displaying a desired graph, range data for determining the display range of the graph, etc.
c is operated when inputting the functional formula "Y=F(X)" in the orthogonal coordinate system, and the "r=" key 12d is operated when inputting the functional formula "r=g(θ)" in the polar coordinate system. be operated on. Also,
The "range" key 12e is operated when setting the range mode for inputting the range data, and the "graph" key 12f is operated when displaying a graph based on each of the above function formulas on the display screen. Ru.

Further, the "trace" key 12g is operated to trace the locus of the graph displayed on the display screen, and the "→" key 12h is operated to move the trace position. ↓" key 12i is operated when switching the graph to be traced.

The control unit 11 is equipped with a flag register 11a, and flag data F of the flag register 11a is set to "2" when tracing the graph in the orthogonal coordinate system, and when tracing the graph in the polar coordinate system. Set to “1” during tracing.

The above formula memory 13 stores the above “Y=” key 1.
Cartesian coordinate code “Y=” selected according to the operation of 2c
The orthogonal coordinate system functional formula storage area 13a corresponding to
Polar coordinate system functional formula storage area 13b corresponding to the polar coordinate code "r=" selected according to the operation of the "r=" key 12d
The functional formula data inputted following the operation of the "Y=" key 12c is stored in the Cartesian coordinate system function formula storage area 13a, and the data inputted following the operation of the "r=" key 12d. The functional formula data to be calculated is stored in the polar coordinate system functional formula storage area 13b.

The data memory 14 has a range data register 14a, an orthogonal coordinate system register 14b, and a polar coordinate system register 14c.
4a contains range data indicating the display range of the graph on the display screen, that is, the minimum and maximum coordinates "Xmin" and "Xmax" at the left and right ends of the X-axis display screen.
”, the minimum and maximum coordinates “Ymin” and “Ymax” at the bottom and top ends of the Y-axis on the display screen are respectively set and stored by the key input unit 12.

The orthogonal coordinate system register 14b also stores the true coordinates X and the true coordinates A predetermined amount of update data ΔX of , and true coordinates Y obtained based on the true coordinates X are stored.

Further, the polar coordinate system register 14c stores the θ value for the polar coordinate system function formula "r=g(θ)", the predetermined amount update data Δθ of the θ value, and the r value obtained based on the θ value. be remembered.

[0021] Here, the graph of the orthogonal coordinate system is the true coordinate data (X, Y )
is converted into display coordinate data (x, y) with the lower left corner on the display screen as the reference point and displayed.

[0022] In addition, the graph of the polar coordinate system is based on the θ value and r
After converting the values into true coordinate data (X, Y) based on the origin of the X-axis and Y-axis based on the following equations 1 and 2,
Further, as described above, the data is converted into display coordinate data (x, y) with the lower left corner of the display screen as the reference point and displayed. X=r cosθ...Equation 1 Y=r sinθ...Equation 2

The calculation unit 15 starts calculation processing based on the functional formula stored in the formula memory 13, and performs coordinate conversion calculation processing from the true coordinate data (X, Y) to display coordinate data (x, y). , data conversion calculation processing from the polar coordinate data (θ, r) to true coordinate data (X, Y), and
The display coordinate data ( x, y) is the graph display buffer 16b
is plotted.

Here, the true coordinates X corresponding to each display coordinate x on the dot matrix on the display section 17 are obtained by the following equation 3, and the display coordinates corresponding to the true coordinates Y obtained based on the true coordinates y is determined by the following equation 4. X=(Xmax-Xmin)(x-1)/(M
-1)+Xmin...Equation 3 However, M is the number of dots on the X axis in the display section 17, "96". y=(Y-Ymin)(N-1)/(Ymax
-Ymin)+1...Formula 4 However, N is the number of dots on the Y axis in the display section 17, "64".

The text and graph display buffer 16
a and 16b each have a memory area corresponding to the number of screen dots in the display section 17, and when display data is written to the text and graph display buffers 16a and 16b, the writing position of the display data is Display processing is performed on the dot matrix of the corresponding display section 17. That is, when the display coordinate data (x, y) calculated by the calculation section 15 is plotted on the graph display buffer 16b, the display section 1 corresponding to the plot position
Coordinates will be displayed for the two-dimensional coordinates on 7.

In this case, the coordinate points on the display section 17 that are in the plotting state by the calculation section 15 are displayed blinking when the graph trace mode is set based on the operation of the "trace" key 12g.

Here, when two or more display coordinate data (x, y) are plotted in the graph display buffer 16b, a graph consisting of each coordinate data connecting the previous plot position and the current plot position is displayed. Display data is
Both data are preset from the calculation section 15 into the graph display buffer 16b. The display section 17 is, for example, 96×64
It is constructed using a liquid crystal display device with a dot matrix display method. On the other hand, the key input data and function formula data are written into the text display buffer 16a and displayed on the display section 17. Next, the graph display operation of the small electronic calculator with graph display function configured as described above will be explained.

[0028] When the user inputs “Y=
” key 12c, numerical/character key 12a, function key 12
By manipulating b, first, the orthogonal coordinate system function formula “Y=F(X)
”, the input function formula “Y=F(X)”
is the orthogonal coordinate code “
Y=" is stored in the orthogonal coordinate system functional formula storage area 13a.

Furthermore, by operating the "r=" key 12d in the key input unit 12, the polar coordinate system function formula "r=g(θ)" is input.
, the input function equation "r=g(θ)" is converted into the polar coordinate code "r=g(θ)" in the equation memory 13 by the control unit 11.
” is stored in the polar coordinate system functional formula storage area 13b.

In order to display a graph according to each of the above-mentioned function formulas, the range mode is set by operating the "range" key 12e in the key input section 12, and the graph is displayed by operating the numerical/character keys 12a. Range data indicating the display range of Xmin, Xmax, Ymin, Y
Enter max. This range data Xmin,X
max, Ymin, and Ymax are stored in the range data register 14a of the data memory 14 by the control unit 11.

That is, when the "graph" key 12f in the key input section 12 is operated to display a graph, the orthogonal coordinate code "Y=" set in the formula memory 13 is first read out by the control section 11. Cartesian coordinate system functional formula ``
The process moves on to graph display processing of ``Y=F(X)''.

Then, the true coordinates X in the orthogonal coordinate system register 14b of the data memory 14 are set to the minimum coordinates Xmin set in advance in the range data register 14a, and the arithmetic processing regarding the above "Y=F(X)" is performed. It is executed in section 15. This calculation unit 15 calculates the above “
When true coordinate data (X, Y) regarding "Y=F(X)" is obtained, display coordinate data (x, y) corresponding to the true coordinate data (X, Y) is obtained based on Equations 3 and 4 above. The calculated value is plotted from the arithmetic unit 15 to the graph display buffer 16b, and is also displayed on the display unit 17.

Here, the current true coordinates X in the orthogonal coordinate system register 14b are updated according to the predetermined amount update data ΔX, and the arithmetic processing regarding the above "Y=F(X)" is performed again in the arithmetic unit 15. executed.

That is, the process of updating ΔX of the true coordinates X, and ``Y=F(X
)” and the calculated true coordinate data (X
, Y) to display coordinate data (x, y), the above preset display coordinate range Xmi
The orthogonal coordinate system function equation “Y=F
(X)" graph display processing is now performed.

After that, the display coordinate range Xmin,
The orthogonal coordinate system function formula “Y=F(X)” corresponding to Xmax
When the graph display process of `` is completed, the next coordinate system code set in the formula memory 13 is read out by the control unit 11.

When the coordinate system code "r=" set next to the orthogonal coordinate code "Y=" is read from the formula memory 13, the θ value in the polar coordinate system register 14c of the data memory 14 becomes the initial value "0". ”, and the above “r=g(θ
)” is executed by the calculation unit 15. When polar coordinate data (r, θ) is obtained through this calculation process, the polar coordinate data (r, θ) is
is converted into true coordinate data (X, Y). Then, based on equations 3 and 4 above, the true coordinate data (
Display coordinate data (x, y) corresponding to the coordinates (x, y) are obtained, plotted from the calculation section 15 onto the graph display buffer 16b, and displayed on the display section 17.

Here, the current θ value in the polar coordinate system register 14c is the predetermined amount update data Δθ (for example, π
/10), and the above “r=g(θ)” is updated again.
The arithmetic processing related to this is executed in the arithmetic unit 15.

That is, the Δθ update process of the θ value, the calculation process of "r=g(θ)" based on the updated θ value, and the true coordinate data ( By repeating the conversion process to display coordinate data (x, y) and the conversion process to display coordinate data (x, y), the polar coordinate system function formula "r=g( θ)" graph display processing is now performed.

After this, in the formula memory 13, if there is no functional formula after the orthogonal coordinate system function formula "Y=F(X)" and the polar coordinate system function formula "r=g(θ)", This means that graphs corresponding to all the functional formulas written in the formula memory 13 are displayed on the display section 17. FIG. 2 is a diagram showing the display state of the display section 17 accompanying graph display processing and graph tracing processing of this small electronic calculator with a graph display function.

FIGS. 3 and 4 are flowcharts showing the graph tracing process of this small electronic calculator with a graph display function. When the "trace" key 12g in the key input section 12 is operated to perform graph tracing, the control The coordinate system code of the first equation set in the equation memory 13 is read out by the unit 11, and it is determined whether it is the orthogonal coordinate code "Y=" or the polar coordinate code "r=" (steps S1, S2).
.

First, the orthogonal coordinate code "Y=" is read out from the formula memory 13 of this embodiment, and the process shifts to tracing processing for the orthogonal coordinate graph. Here, flag data "F=2" is stored in the flag register 11a in the control unit 11.
” is set (step S3).

Then, the true coordinate X in the orthogonal coordinate system register 14b of the data memory 14 is set to the minimum coordinate Xmin preset in the range data register 14a, and Arithmetic processing is executed in the arithmetic unit 15 (steps S4, S
5).

When the true coordinate data (X, Y) is obtained through the arithmetic processing in step S5, display coordinate data (x, . (Step S6).

Here, when the "→" key 12h in the key input section 12 is operated, the control section 11 determines whether the flag data F in the flag register 11a is "1" or "2", that is, the current graph to be traced. It is determined whether the graph is a polar coordinate graph or a rectangular coordinate graph (steps S7, S8).

In this case, in step S8 above, F=2,
In other words, it is determined that the Cartesian coordinate graph is being traced,
The current true coordinates X in the orthogonal coordinate system register 14b are updated according to the predetermined amount update data ΔX, and the calculation process regarding the above "Y=F(X)" is executed again in the calculation unit 15 (step S9 →S5).

That is, by repeating the processing in steps S5 to S9, the orthogonal coordinate system function equation "Y
The trace display process of the graph locus corresponding to "=F(X)" is sequentially performed.

On the other hand, during the trace display process of the orthogonal coordinate graph in steps S5 to S9, for example, with the coordinate point a1 in FIG. 2 as the trace point, the trace point update process by operating the "→" key 12h To switch the graph to be traced from the rectangular coordinate graph to the polar coordinate graph without performing
2i, it is determined "No" in step S7 and "Yes" in step S10, and the control unit 1
1 specifies the coordinate system code of the following equation set in the equation memory 13 (step S11).

That is, the polar coordinate system function equation "r=g(θ)" in the equation memory 13 is specified, and here, in the control section 11, the flag data F in the flag register 11a is set to "1" or "2". In other words, it is determined whether the graph to be traced last time is a polar coordinate graph or a rectangular coordinate graph (
Step S12).

In this case, in step S12 above, F=2
In other words, it is determined that the orthogonal coordinate graph was traced last time, and it is further determined whether the next functional formula in the formula memory 13 designated in step S11 is a functional formula of the orthogonal coordinate system (step S13). ).

If "No" in this step S13, that is, it is determined that the next functional expression specified in the above step S11 is a polar coordinate system, the tracing process of the orthogonal coordinate graph is changed to the tracing process of the polar coordinate graph. Transition.

That is, first, at the point in time when the "↓" key 12i is operated corresponding to the determination in step S10, that is, at the time when the switching operation of the graph to be traced is performed, the true value corresponding to the trace point a1 of the orthogonal coordinate graph is The coordinates (X, Y) are read from the orthogonal coordinate system register 14b to the calculation unit 15, and the angle θ "=tan-1 (Y/X)" of the trace point a1 with respect to the coordinate origin is calculated (step S14).

Here, the flag data F of the flag register 11a in the control unit 11 is set to "1" indicating that the tracing process of the polar coordinate graph is in progress (step S15).

Then, the origin angle θ corresponding to the trace point a1 of the orthogonal coordinate graph calculated by the arithmetic unit 15 is determined by the polar coordinate system function equation ``r=g(θ )" and the arithmetic processing is executed (step S16).

When the polar coordinate data (r, θ) is obtained through the arithmetic processing in step S16, the above formulas 1 and 2
Based on
X, Y) (step S17). Then, based on Equation 3 and Equation 4, display coordinate data (x, y) corresponding to the true coordinate data (X, Y) obtained in step S17 is determined, and the display coordinate data (x, y) is obtained from the calculation unit 15 in the graph display buffer 16b. At the same time, the coordinate point b1 is displayed blinking on the display unit 17, and the polar coordinate data (
r, θ) are displayed in the empty area (step S1
8). As a result, trace point b1 of the polar coordinate graph based on trace point a1 of the orthogonal coordinate graph
This means that the graph to be traced has been switched to .

Here, when the "→" key 12h in the key input section 12 is operated, the control section 11 determines whether the flag data F in the flag register 11a is "1" or "2", that is, the current graph to be traced. It is determined whether the graph is a polar coordinate graph or a rectangular coordinate graph (steps S7, S8).

In this case, in step S8 above, F=1,
In other words, it is determined that the polar coordinate graph is being traced, the current θ value in the polar coordinate system register 14c is updated according to the predetermined amount update data Δθ, and the above “r=
The arithmetic processing regarding "g(θ)" is executed in the arithmetic unit 15 (steps S19→S16).

[0057] That is, the above steps S16 to S18,
By repeating the process execution in S7, S8 → S19,
The trace display process of the graph locus corresponding to the polar coordinate system functional expression "r=g(θ)" is sequentially performed.

On the other hand, the above steps S16 to S18, S7
, S8→S19, during the trace display process of the polar coordinate graph, for example, with the coordinate point b2 in FIG. When the "↓" key 12i is operated to switch the graph from the polar coordinate graph to the rectangular coordinate graph, step S
"No" in step S10, "Yes" in step S10.
”, and the control unit 11 specifies the coordinate system code of the following equation set in the equation memory 13 (step S11
).

That is, the orthogonal coordinate system function formula "Y=F(X)" in the formula memory 13 is specified, and here,
The control unit 11 determines whether the flag data F of the flag register 11a is "1" or "2", that is, whether the previous graph to be traced is a polar coordinate graph or a rectangular coordinate graph (step S12).

In this case, in step S12 above, F=1
In other words, it is determined that the polar coordinate graph was traced last time, and it is further determined whether the next functional formula in the formula memory 13 specified in step S11 is a functional formula of the orthogonal coordinate system (step S20). .

[0061] In this step S20, "Yes",
That is, when it is determined that the next functional expression specified in step S11 is in the orthogonal coordinate system, the process shifts from the tracing process of the polar coordinate graph to the tracing process of the orthogonal coordinate graph.

That is, the polar coordinate data (r , θ) are read out from the polar coordinate system register 14c to the calculation unit 15, and the true coordinates X corresponding to the trace point b2 are calculated based on the equation 1 (step S
21).

Here, the flag data F of the flag register 11a in the control unit 11 is set to "2" indicating that the tracing process of the orthogonal coordinate graph is in progress (step S22).

Then, the true coordinates X corresponding to the trace point b2 of the polar coordinate graph calculated by the arithmetic unit 15 are determined by the orthogonal coordinate system function equation "Y=F(X )” is assigned to
The calculation process is executed (step S5).

When the true coordinate data (X, Y) is obtained through the arithmetic processing in step S5, display coordinate data (x, . (
Step S6). This means that the graph to be traced has been switched from the trace point b2 of the polar coordinate graph to the trace point a2 of the orthogonal coordinate graph.

On the other hand, in step S13, "Ye
s", that is, when switching from tracing processing of a Cartesian coordinate graph to tracing processing of another Cartesian coordinate graph, the true coordinates X)", a new trace point is obtained in steps S5 and S6.

[0067] Also, in step S20 above, "No.
”, that is, when switching from tracing processing of a polar coordinate graph to tracing processing of another polar coordinate graph, the θ value corresponding to that trace point is substituted as is into the next polar coordinate system function formula “r=g(θ)”. As a result, new trace points are found in steps S16 to S18.

Furthermore, in step S2, “No.
”, that is, the coordinate system code of the first equation is the polar coordinate code “r
=", tracing processing for that polar graph is executed first. Here, flag data "F=1" is stored in the flag register 11a in the control unit 11.
is set (step S23).

Then, the θ value in the polar coordinate system register 14c of the data memory 14 is set to the initial value "0", and the calculation process regarding the polar coordinate system function formula "r=g(θ)" is executed in the calculation unit 15. (Step S24→S16). Then, as described above, trace points for this polar coordinate graph are determined through steps S17 and S18, and the coordinate points are displayed blinking on the display section 17.

Therefore, according to the small electronic calculator with the graph display function configured as described above, the orthogonal coordinate system functional formula "Y=
Graph corresponding to “F(X)” and polar coordinate system functional formula “r=g
(θ)'' can be displayed together on the same screen on the display unit 17, and graph tracing can be performed in which one graph is associated with the other graph at its trace point, so that the intersection point can be , contacts, etc. can be easily analyzed.

[0071]

[Effects of the Invention] As described above, according to the present invention, the device has a dot matrix type display section, displays an input function equation in a graph form, and has a function of tracing the trajectory of the displayed graph. , a function formula input means for inputting a function formula in a rectangular coordinate system and a function formula in a polar coordinate system, and a graph corresponding to the function formula in a rectangular coordinate system and a function formula in a polar coordinate system respectively inputted by this function formula input means. A graph display means for displaying a graph in a mixed manner on a display section, a tracing means for tracing one of the orthogonal coordinate system graph and a polar coordinate system graph displayed by the graph display means, and a graph to be traced by the tracing means for tracing the other graph. trace switching means for switching to a graph of

When the graph to be traced is switched from one graph to another by this trace switching means, an adjustment is made to calculate one parameter of the coordinate system corresponding to the other graph based on the trace point of the one graph. Coordinate system parameter calculation means,

trace point designating means for assigning the value of the parameter obtained by the different coordinate system parameter calculating means to the functional formula of the other graph coordinate system to designate a new trace point;

Since the present invention is configured with the following, it becomes possible to trace the graphs in association with each other, especially when a rectangular coordinate graph and a polar coordinate graph are displayed together on the same screen.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an electronic circuit of a small electronic calculator with a graph display function according to an embodiment of the present invention.

FIG. 2 is a diagram showing the display state of the display unit associated with graph display processing and graph tracing processing of the small electronic calculator with a graph display function.

FIG. 3 is a first flowchart showing graph tracing processing of the small electronic calculator with graph display function.

FIG. 4 is a second flowchart showing graph tracing processing of the small electronic calculator with graph display function.

[Explanation of symbols]

11...Control unit, 11a...Flag register, 12...Key input unit, 12a...Numeric/character keys, 12b...Function key, 1
2c... "Y=" key, 12d... "r=" key, 12e...
"Range" key, 12f..."Graph" key, 12g..."
Trace" key, 12h..."→" key, 12i..."↓"
key, 13...formula memory, 13a...orthogonal coordinate system functional equation storage area, 13b...polar coordinate system functional equation storage area, 14...data memory, 14a...range data register, 14b...
Orthogonal coordinate system register, 14c...Polar coordinate system register, 15
...Arithmetic section, 16a...Text display buffer, 16b...Graph display buffer, 17...Display section.

Claims (1)

[Claims] 1. A small electronic calculator with a graph display function, which has a dot matrix type display section, displays an input function equation in a graph form, and has a function to trace the trajectory of the displayed graph. A function formula input means for inputting the function formula of the system and the function formula of the polar coordinate system, and graphs corresponding to the orthogonal coordinate system function formula and the polar coordinate system function formula inputted by the function formula input means, respectively, are displayed on the display section. A graph display means for displaying a mixture of graphs, a tracing means for tracing one of the orthogonal coordinate system graph and a polar coordinate system graph displayed by this graph display means, and a graph to be traced by this tracing means on another graph. a trace switching means for switching, and when the trace switching means switches a graph to be traced from one graph to another, one parameter of a coordinate system corresponding to the other graph is set based on the trace point of the one graph; a different coordinate system parameter calculating means for calculating; a trace point specifying means for specifying a new trace point by substituting the value of the parameter obtained by the different coordinate system parameter calculating means into the functional formula of the other graph coordinate system; A small electronic calculator with a graph display function.