Graphics |

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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