Graph Plotting Application
by Ben Avison, Brian Daulton and Mark Moxon

The GraphPlot application enables Cartesian and polar graphs to be generated in the form of Draw files.

Running the application installs an icon on the icon bar, and clicking on this icon opens the main window, which contains a number of sections. There are two radio icons marked Cartesian and Polar, and clicking on each of these changes the type of graph generated by the application. 

Before describing the differences between the two options, it is important to know how to save your graph. When all the details have been entered, you can either drag the Draw file from the Save section of the window to a directory viewer (where it will be saved as a Draw file under the name in the writable icon) or to the drawing you are creating; in the latter case the graph will then appear in the drawing. The position of the pointer when you release the Select button will define where the graph will appear.

To remove GraphPlot from the icon bar, simply click Menu over the icon bar icon and choose the Quit option from the menu.

Cartesian Graphs
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The Cartesian option enables graphs using Cartesian co-ordinates to be generated. The function to be plotted should be entered into the 'Function of X: Y =' writable icon as a function of X (e.g. SIN(X) to plot a sinusoidal curve). The minimum and maximum values of X and Y should then be entered in the next four icons (negative or positive integers only), the X-increment should be entered in the next icon, and you can then choose whether to have the grid drawn via the option icon. Movement between the various icons is by the up/down cursor keys and Return.

The axes are drawn whether or not you ask for a grid, and any vertical asymptotes are drawn as dotted lines. If you specify no grid, marks are made on the axes to help you add scales in Draw. Graphs of equations of the form Y=f(X) can be drawn by entering the function as SQR(f(X)).

Up to 5 graphs may be drawn on the same axes by entering a colon between the functions in the function icon, e.g. entering X-3:4*X+7 will cause the graphs of Y=X-3 AND Y=4X+7 to be drawn on the same axes. When more than one function is specified, the one entered first is drawn with a full line and the others with a variety of dotted lines.

Polar Graphs
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The Polar option enables graphs using polar co-ordinates to be generated. The function to be plotted should be entered into the 'Function of T: R =' writable icon as a function of T (e.g. 1+T).

The maximum size of the function should then be entered in the 'Max R' icon (to enable the graph to be scaled), the number of line segments to be produced in the plot should be entered in the next icon (to avoid very detailed plots), and you can then choose whether you require scale circles and/or radial lines to be drawn, and whether you want negative values of R to be plotted, all through the option icons in the Polar section.

The function for the graph is entered as a function of T. In polar geometry, R is the distance of the point from the origin, and T (which stands for Theta) is the angle of the line joining the origin and the point, measured in radians.

Up to 3 separate graphs can be drawn on the same axes by enterering a colon (":") between the functions in the first window, as for the Cartesian section. 

 RISC User 1992
