Re: fast scatter plots - advice sought

[John W. Eaton]

On 11-Jan-2010, Jaroslav Hajek wrote:

| On Mon, Jan 11, 2010 at 7:35 PM, John W. Eaton <address@hidden> wrote:
| > On 11-Jan-2010, Robert T. Short wrote:
| >
| > | The way things are done now, scatter is useless for more than a very
| > | small number of points and I think MATLAB compatibility should be
| > | dropped if uselessness is the result of compatibility.  However, it
| > | sounds like we are NOT currently compatible with MATLAB and becoming
| > | compatible might fix the problem.
| >
| > I think all that needs to be done at this point to make it compatible
| > and faster is to change the breakpoint to 100
| 
| I disagree with that. The value of 100 is not documented anywhere and
| can probably be changed anytime by some MathWorks developer that will
| adjust the code. I think it's a plain nonsense to pursue Matlab
| compatibility to this extent.
| 
| > and use patch instead of
| > line objects.
| >
| 
| This is similar. The documentation  doesn't seem to say anything about
| patch objects. To me, it seems logical to use the simplest primitive
| capable of plotting a set of points, which I think is a line. Are
| patches somehow faster or otherwise superior to lines? If yes, why?

As David says, this used to work in Octave:

  n=100; x=randn(1,100);y=randn(1,100);c=sqrt(x.^2+y.^2); 
  scatter(x,y,2,c); colormap hot

and now it does not.  It also works in Matlab.  So please restore the
use of patch insteaad of line.

I don't care so much about whether the breakpoint is 20 or 100, but
since someone discovered that it is 100 in Matlab, why not change it?

jwe