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Plotting Applet - Editorial Review

Philippe B. Laval

This general Java applet can be used in a variety of settings whenever a graph needs to be displayed and analyzed.  The functions are input in very standard notation, but there is a help screen on syntax available if there are any doubts.  Up to ten functions can be shown simultaneously, and a color legend is displayed to keep them straight.  At any time, one function is designated as "active" and the trace feature can be applied to that graph.  The idea of the trace is elegant -- click on any point and the trace point with the same x-coordinate as the mouse click will appear on the graph of the active function.  Zooming is similarly accomplished by dragging a selection box around the area of interest. 

As with any general tool, there are quirks to get used to.  Distinguishing between a mouse click and the dragging a very tiny selection area is subtle and this applet can be confused, leading to meaningless zooms when a trace was intended.  There is no "undo" button for such errant events, but there is a "reset" button that ultimately saves the day by putting everything back in a standard window.  Overall the simplicity of the design outweighs these minor issues to give a highly useable, versatile online graphing applet.

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