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 ¹/10 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