# How to make a a certain range with different color in colorbar

10 views (last 30 days)
Yaser Khojah on 8 Aug 2020
Commented: Walter Roberson on 12 Aug 2020
I created a a contour plot and I would like to make the range between -50 and 0 different than the range 0 and 50 as below. Anway to help please
[X,Y] = meshgrid(10:5:80,0:1:20);
Z = f([X(:), Y(:)]);
Z1 = reshape(Z,[21,15]);
figure
contour(X,Y,Z1,15000)
colormap hsv
colorbar
xlabel('\gamma (%)')
ylabel('\lambda (%)')
zlabel('m^{*}_{NPV} (\$B)')

Sudheer Bhimireddy on 8 Aug 2020

Yaser Khojah on 9 Aug 2020
It is better but wanted to show how it vareis between 0 and 50.
Sudheer Bhimireddy on 9 Aug 2020
First, your cmap array will be of size Nx3.
If I understand you correctly, you want to show the variation between 0 and 50, but not from 50 to 300.
If you have the indices for 0 and 50, you can edit the cmap array between the corresponding indices to show the variation and then can have same color for thereafter. Also know, that sometimes limiting the coloraxis (caxis([cmin cmax])) could be useful. If you want anyvalue after 50 to have the same color then caxis([min(z) 50]) will do the trick.
For Option 1, colormapeditor is a gui based method, so it is purely manual.
Yaser Khojah on 9 Aug 2020
Thanks Sudheer, I want exactly what I have with additional variation between 0 and 50. The range is very small which I’m struggling to present.

Walter Roberson on 9 Aug 2020
The above function requires that the positions be defined in relative terms, 0 to 1, rather than in absolute terms. You would have to decide ahead of time what your caxis() is going to be, and use proportional positions through that range,
relative_position = (data_x - min_to_map)./(max_to_map - min_to_map)

Walter Roberson on 12 Aug 2020
Yaser Khojah on 12 Aug 2020
Oh I’m sorry I just added the xsl for you since I though I can’t upload the mat file.
Walter Roberson on 12 Aug 2020
levels = [-700 -600 -500 -400 -300 -200 -100 -50 -40 -30 -20 -10 0 10 20 30 40 50 100 200 300];
[a,b] = contourf(X, Y, Z1, levels);
This will not in itself create new colormap entries for the various levels, but it will outline them more clearly.
To create new colormap entries, you have to follow the strategy I outlined above, of creating a colormap with replicated slots.