Graphics

Interactive Plotting

The ginput function enables you to use the mouse or the arrow keys to select points to plot. ginput returns the coordinates of the pointer's position, either the current position or the position when a mouse button or key is pressed. See the ginput function for more information.

Example -- Selecting Plotting Points from the Screen

This example illustrates the use of ginput with the spline function to create a curve by interpolating in two dimensions.

First, select a sequence of points, [x,y], in the plane with ginput. Then pass two one-dimensional splines through the points, evaluating them with a spacing one-tenth of the original spacing.

• axis([0 10 0 10])
  hold on
  % Initially, the list of points is empty.
  xy = [];
  n = 0;
  % Loop, picking up the points.
  disp('Left mouse button picks points.')
  disp('Right mouse button picks last point.')
  but = 1;
  while but == 1
      [xi,yi,but] = ginput(1);
      plot(xi,yi,'ro')
      n = n+1;
      xy(:,n) = [xi;yi];
  end
  % Interpolate with a spline curve and finer spacing.
  t = 1:n;
  ts = 1: 0.1: n;
  xys = spline(t,xy,ts);
  
  % Plot the interpolated curve.
  plot(xys(1,:),xys(2,:),'b-');
  hold off
  

This plot shows some typical output.

Displaying Contours in Polar Coordinates

Animation

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