How to make one contour transparent in contourf?

Hello, I have a contour plot with several layers define as follows:

[c,h]=contourf(X,Y,Z,[value1 value2 value3 value4]);

I would like to make a selected contour transparent, let's say the first contour defined by value1. Any thought on how to proceed? Thanks.

Arnault

Answer 1

[José-Luis]

[C,h] = contourf(peaks(20),-4:1:4);
allH = allchild(h);
valueToHide = 1;
patchValues = cell2mat(get(allH,'UserData'));
patchesToHide = patchValues == valueToHide;
set(allH(patchesToHide),'FaceColor','k','FaceAlpha',0.8);

Note that you could set the FaceColor to white if that is what you mean by transparent. Otherwise you could set the FaceAlpha to zero for the patch to be transparent.

Please accept an answer if it helps you.

[Walter Roberson]

Due to round-off error, it is best not do do exact comparisons of floating point values.

patchesToHide = abs(patchValues - valueToHide) < 100*eps(valueToHide);

[Arnault]

Thanks, works well!

[Arnault]

I have a related question. The colorbar keeps the original color. Any idea on how I could do the same on the colorbar?

Answer 2

[Will Grant]

See my answer here - working for R2020a

Answer 3

[Leslie]

This solution has stopped working in 2014b. Does anyone know if we still change the tranparency of 2D contour plots? If so how? Thanks

[Boris Belousov]

Unfortunately you have to manually define a contour of the area you want to make transparent. See how to make contour plots transparent.