[Matplotlib-users] colormap from blue to transparent to red

[Stefan M. <ste...@mn...>]

Hi everyone, 

I am having trouble with colormaps unsing pcolormesh. I would like to
plot and colorise a seismic wave field above a map. Plotting works fine
but I do not know how to bring transparency into colormaps. For negative
values I want the coloration being blue then it should become
transparent and the greatest value should be drawn red. I have tried a
lot but without any success. As far as I can see, the keyarg alpha does
not fit my needs at all. 

Do you have any suggestions for me? 

Regards

Stefan