Thread: [Matplotlib-users] add colors to scatter plots

Hi,
I am simulating the movement of some particles that carry some
concentration of different species. Those concentrations change in time
and space and I would like to be able to see their distribution in
space. 
I am using the scatter plot of Matplotlib to plot the position of each
particle. That works great, but when I try to assign different colors to
each dot according to their concentration I find some problems. Although
there is a big range of concentrations (colors) I can only see two in
the plot. Is it possible to define more intervals to assign the colors?
I think I did not understand the right way to define the c array
intensities when I use the command: 
scatter(self, x, y, s=None, c)
How should I generate that array? I looked at the example but I couldn't
figure it out.
Thanks for your help,
I look forward to see the future versions of Matplotlib. So far, it
looks very good.
Paulo.

>>>>> "paulo" == paulo <phe...@eo...> writes:
 paulo> I am using the scatter plot of Matplotlib to plot the
 paulo> position of each particle. That works great, but when I try
 paulo> to assign different colors to each dot according to their
 paulo> concentration I find some problems. Although there is a big
 paulo> range of concentrations (colors) I can only see two in the
 paulo> plot. Is it possible to define more intervals to assign the
 paulo> colors? I think I did not understand the right way to
 paulo> define the c array intensities when I use the command:
 paulo> scatter(self, x, y, s=None, c) How should I generate that
 paulo> array? I looked at the example but I couldn't figure it
 paulo> out.
Hi Paulo,
It would help to see some code to let you know why your current
approach isn't working. For now, all I can say is that c should be a
len(x) Numeric array of concentrations. It might help for you to do
 hist(c, 100) 
to look at the distribution of concentrations. If the distribution is
bimodal and strongly peaked, this may explain why you only see two
colors.
As for your question about defining more colors, the default is to use
a colormap of 1000 colors, which should be an ample number to see a
range unless something funny is going on with your c array.
When you post some code, also post the first few entries of c, eg
c[:10].
JDH