Plot points (x,y) and use a third (z) as the color code in Matlab

Question

Possible Duplicate:
matlab: scatter plots with high number of datapoints

I have 3 vectors of 315,000 elements each. X,Y, and Z. X & Y are coordinates and Z is a value. I must plot the coordinates as points in a 2D graph, the Z is a color indicator at each coordinate of X and Y. I've tried the "scatter" command, but it extremely slow. Would anybody suggest a better way?

thanks!

Solution

Depending on what kind of color map you are looking for, you can try something like

zmin=min(Z);
zmax=max(Z);
map=colormap;
color_steps=size(map,1);

hold on
for i=1:color_steps
    ind=find(Z<zmin+i*(zmax-zmin)/color_steps & Z>=zmin+(i-1)*(zmax-zmin)/color_steps);
    plot(X(ind),Y(ind),'o','Color',map(i,:));
end

The finding is a little expensive but it seems to be quicker than scatter. I'm sure you could optimize this further.

Comments

[Oliver Amundsen]

I'm trying to plot the elements as points.... but thanks for the comment. I'll update the question