Mega Code Archive
Input the function and draw the curve
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/*************************************************************************
* *
* This source code file, and compiled classes derived from it, can *
* be used and distributed without restriction, including for commercial *
* use. (Attribution is not required but is appreciated.) *
* *
* David J. Eck *
* Department of Mathematics and Computer Science *
* Hobart and William Smith Colleges *
* Geneva, New York 14456, USA *
* Email: eck@hws.edu WWW: http://math.hws.edu/eck/ *
* *
*************************************************************************/
import java.awt.*;
import edu.hws.jcm.data.*;
import edu.hws.jcm.draw.*;
import edu.hws.jcm.awt.*;
public class GraphApplet1 extends java.applet.Applet {
public void init() {
Parser parser = new Parser(); // The Parser will take the user's input
// and turn it into an Expression. By
// default, a Parser knows about the
// constants pi and e, the basic arithmetic
// operations + - * / ^ (where ^ is
// exponentiation), standard functions
// (sin, cos, tan, sec, csc, cot, sqrt,
// cubert, abs, ln, log2, log10, exp,
// trunc, round, floor, ceiling, arcsin,
// arccos, arctan). There is also a
// conditional "?" operator in the style
// of Java and C++.
Variable x = new Variable("x"); // For the parser to know about the variable x,
parser.add(x); // that variable must be created and added
// to the parser.
DisplayCanvas canvas = new DisplayCanvas();
// A DisplayCanvas is the fundamental JCM class for displaying
// graphical items such as axes and graphs.
canvas.setUseOffscreenCanvas(false); // By default, a DisplayCanvas uses
// "double buffering", which allows for
// smooth animation. However, it does
// use extra memory, so I turn it off
// in this simple applet. You might notice
// that the image flickers a bit when the
// applet is redrawn.
canvas.setHandleMouseZooms(true); // This tells the canvas to let the user
// zoom in and out by clicking, shift-clicking,
// and click-and-dragging on the canvas.
LimitControlPanel limits = new LimitControlPanel();
// A limit control panel can control the x- and y-limits on a DisplayCanvas.
// In the applet, the limit control panel is the gray area containing the
// input boxes for xmin, xmax, ymin, and ymax. It also contains a
// "Set Limits" button (and can contain other buttons if you want). The
// "Set Limits" button is a little redundant because pressing return
// in any of the input boxes will accomplish the same thing. However, it
// has the advantage of giving the user something obvious to do to
// set the limits.
limits.addCoords(canvas); // Tells the LimitControlPanel to control the
// x- and y-limits on this canvas. The limits
// on the canvas and the values in the input
// boxes are synchronized. (Try it by clicking
// on the graph.)
ExpressionInput input = new ExpressionInput("sin(x)+2*cos(3*x)", parser);
// An ExpressionInput is a text-input box where the user can enter
// an expression. The string "sin(x)+2*cos(3*x)" provides the initial
// contents for the box. The parser that is provided as the second
// arguments knows about the variable named "x", which makes it
// possible to use "x" in the expression.
Function func = input.getFunction(x); // To graph, I need a Function, not
// not an expression. input.getFunction(x)
// gets the contents of the ExpressionInput,
// input, considered as a function of the
// variable x.
Graph1D graph = new Graph1D(func); // This represents a graph of the function, func.
// It will be added to the DisplayCanvas,
// which will make it appear on the screen.
JCMPanel main = new JCMPanel(); // The interface for this applet is constructed
// entirely from JCMPanels. This makes much
// of the JCM setup automatic. This constructor
// makes a JCMPanel that uses a BorderLayout.
main.add(canvas, BorderLayout.CENTER); // Add the DisplayCanvas to the panel.
main.add(input, BorderLayout.SOUTH); // Add the ExprssionInput.
main.add(limits, BorderLayout.EAST); // Add the LimitControlPanel.
main.setInsetGap(3); // This leaves a gap of 3 pixels around the edges of the
// panel, where the gray background shows through.
setLayout(new BorderLayout()); // Set up the Applet itself.
add(main, BorderLayout.CENTER);
setBackground(Color.lightGray);
canvas.add( new Axes() ); // Add a set of Axes to the DisplayCanvas. The labels
// on the applet are automatically adjusted when
// the limits on the canvas changes.
canvas.add(graph); // Add the graph to the canvas. It will be redrawn
// whenever necessary.
Controller controller = main.getController();
// A Controller is what makes things happen in a JCM applet. The
// JCMPanel, main, has a controller that recomputes the JCM components
// in the Panel.
controller.setErrorReporter(canvas); // Errors in the user's input need to
// be reported somehow. A Controller can
// have an ErrorReporter for this purpose.
// Currently, the alternatives are to use
// a canvas as an error reporter or to
// use a "MessagePopup". To see an error
// message in the applet, enter any expression
// with a syntax error and press return.
// Note that the blinking input cursor moves
// to the point in the expression where the
// error was discovered.
limits.setErrorReporter(canvas); // A LimitControlPanel also needs a place to
// report errors in the user's input.
main.gatherInputs(); // The JCMPanel must be told to respond to user inputs.
// The gatherInputs() method is an easy way to do this,
// in many cases. In this applet, since there is only one
// input, this is equivalent to the single command
// "input.setOnUserAction(controller)," which tells the
// input object to notify the controller when the user
// presses return in the input box. (Note that input boxes
// in a LimitControlPanel are taken care of automatically.
// They don't need to notify a controller. Also note that
// I couldn't use the gatherInputs(controller) method in
// the previous ArithmeticApplet, since gatherInputs()
// calls the setOnUserAction() method of an input box, but in the
// ArithmeticApplet, I wanted to call setOnTextChange(). The
// difference is that with setOnUserAction(), the controller is
// notified only when the user presses return in the input box
// while with setOnTextChange(), the controller is notified
// each time the text in the input box changes.)
} // end init()
public static void main(String[] a){
javax.swing.JFrame f = new javax.swing.JFrame();
java.applet.Applet app = new GraphApplet1();
app.init();
f.getContentPane().add (app);
f.pack();
f.setSize (new Dimension (500, 500));
f.setVisible(true);
}
} // end class SimpleGraph1
jcm1-source.zip( 532 k)
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