hi,
I recently started some work where I'm going to use scatter plots
heavily with a few thousand points.
I found out, however, that scatter plots were unusably slow with so
many points. This has also been reported before:
http://old.nabble.com/scatter3-is-really-slow-to24312164.htm
by this changeset
http://hg.savannah.gnu.org/hgweb/octave/rev/2f435ed48143
I tried to optimize the plotting strategy to get more reasonable
times, especially in the simplest cases. The old strategy of creating
one object per point is only used for small numbers of points (<= 20).
Otherwise, the points are split into subsets with common color and
size, and these subsets are plotted using a single primitive. This
seems similar to what Matlab does.