# Fill plot with gradient colors

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Sergio Yanez-Pagans on 31 Oct 2021
I'm trying to plot a signal, for example cos(x), with a red gradient colormap for positive values and a blue one for negative values. Something similar to the solution previously discussed in: I haven't been able to make this work for me, any suggestions?
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Sergio Yanez-Pagans on 1 Nov 2021
Thanks Strider!

Dave B on 31 Oct 2021
Edited: Dave B on 31 Oct 2021
Here's one way to make the patch with the color gradient:
x=linspace(0,4*pi,100);
y=cos(x);
patch([x flip(x)],[y zeros(size(y))],[y zeros(size(y))]) You could use jet or turbo to have blue on the bottom and red on the top:
figure
patch([x flip(x)],[y zeros(size(y))],[y zeros(size(y))])
colormap jet Or you could mix hot and cool colormaps:
figure
patch([x flip(x)],[y zeros(size(y))],[y zeros(size(y))])
colormap([cool;hot]) Or you could make your own colormap, just plug in red green and blue values that suit you (first column is red, second column is green, third column is blue):
figure
patch([x flip(x)],[y zeros(size(y))],[y zeros(size(y))])
cmap = ones(256,3);
cmap(129:256,2)=linspace(0,1,128);
cmap(129:256,3)=linspace(0,1,128);
cmap(1:128,1)=linspace(1,0,128);
cmap(1:128,2)=linspace(1,0,128);
colormap(cmap); Sergio Yanez-Pagans on 1 Nov 2021
Thank you Dave, that was really useful!