MATLAB Examples

Move Group of Objects Along Line

This example shows how to move a group of objects together along a line using transforms.

Plot a sine wave and set the axis limits mode to manual to avoid recalculating the limits during the animation loop.

x = linspace(-6,6,1000);
y = sin(x);
plot(x,y)
axis manual

Create a transform object and set its parent to the current axes. Plot a marker and a text annotation at the beginning of the line. Use the num2str function to convert the y-value at that point to text. Group the two objects by setting their parents to the transform object.

ax = gca;
h = hgtransform('Parent',ax);
hold on
plot(x(1),y(1),'o','Parent',h);
hold off
t = text(x(1),y(1),num2str(y(1)),'Parent',h,...
    'VerticalAlignment','top','FontSize',14);

Move the marker and text to each subsequent point along the line by updating the Matrix property of the transform object. Use the x and y values of the next point in the line and the first point in the line to determine the transform matrix. Update the text to match the y-value as it moves along the line. Use drawnow to display the updates to the screen after each iteration.

for k = 2:length(x)
    m = makehgtform('translate',x(k)-x(1),y(k)-y(1),0);
    h.Matrix = m;
    t.String = num2str(y(k));
    drawnow
end

The animation shows the marker and text moving together along the line.

If you have a lot of data, you can use drawnow limitrate instead of docid:matlab_ref.f56-719157 for a faster animation. However, drawnow limitrate might not draw every update on the screen.