Interesting plot behavior

[Robert T. Short]

I use scatter plots regularly in my work, usually with thousands or tens 
of thousands of points.

This little script is a trivial example:


N = 2^14;
stddev = 0.1;

q = 2*((floor(4*rand(N,1))-1.5) + i*(floor(4*rand(N,1))-1.5));
n = stddev*(randn(N,1) + i*randn(N,1));
m =  q + n;
%scatter(real(m),imag(m), 1, 'g');
plot(real(m),imag(m), ".g;;");
axis("square");

Using scatter and tic/toc, it takes 120 seconds to display 2^14 points 
but using plot it is so quick I can't really measure it.

This table gives the times (time until the plot is actually displayed) 
as a function of "N"

2^10  3 seconds
2^11  6 seconds
2^12  14 seconds
2^13  41 seconds
2^14  120 seconds



This was done with octave 3.0, but I get similar behavior using the tip 
(cloned and built yesterday)

Bob
--
Robert T. Short
PhaseLocked Systems