Draw growing circles on a jpeg file.

I have read in a jpeg file of a floor map. Now I want to draw a circle on it of time-dependent radius, so that it appears to be growing with time. I used the function viscircles. At a later time I want to go to a different position within the image and start drawing a new circle. But viscircles draws a filled circle that is persistent. How can I plot new circles and make the earlier circle go away. I could use cla every time I want a new circle, but that would require me to display the background image again. That would add processing time.

Answer 1

[Jan]

You can remove the object by the delete command:

image(rand(640, 480, 3) * 0.5);
h = viscircles([200, 200], 5);
pause(1)
delete(h);

[Ranjan Sonalkar]

Thanks, works as I would like it to.

Answer 2

[Geoff Hayes]

Ranjan - according to viscircles, if you do something similar to

 hg = viscircles(ax,centers,radii)

then h is a handle to an hggroup object. As such, you should be able to hide these circles (if you wish by setting the Visible property to off, see hggroup properties) or you should be able to just delete this object

 delete(hg)

The following example illustrates this

   hg = hggroup;
   x = -2*pi:0.4:2*pi;
   y = sin(x);
   line(x,y,'Parent',hg)

The sine curve is drawn and then we can delete is with

   delete(hg)

[Ranjan Sonalkar]

Thanks, works as I would like it to.