erasing symbols

I'm working on a little tool using callbacks, so I have it set up so that
I can interactively add special points in the plot window. I would also
like to delete points. I tried writing a white '+' on top of my original '+'
but it looks like the dithering causes the original point to only fade a
bit, and not disappear. I tried overwriting circles ('o'), and the interiors
disappeared, but I'm left with the border.

Any suggestions on how to do this? I thought it was going to be easy!

I guess I could just save all the commands and do a redraw, but I'd like
to avoid that if I can.



Alan K. Jackson | To see a World in a Grain of Sand |
alan@...895... | And a Heaven in a Wild Flower, | | Hold Infinity in the palm of your hand |
Houston, Texas | And Eternity in an hour. - Blake |