MATLAB Answers


Maximum scaling resolution of colormap for colorbar to be correct

Asked by Hannes Mogensen on 2 Dec 2016
Latest activity Commented on by David Goodmanson on 5 Jan 2017
I am experimenting with a function for using several colormaps in the same surface plot - e.g one colormap scaling for values < 0, another one for values between 0 and 1 and a third for values > 1.
I have used the following code as a proof of concept:
[x, y, z] = peaks(30);
surface(x, y, z);
n1 = 512;
n2 = 512;
cbar_mapping = [spring(n1); bone(n2)];
The function above generates the following figure.
In the final function I will set the values of variables n1, n2, ... , so that the relative contribution of each colormap will be assigned to the different regions of z, as described above. The higher the total value of n1 + n2+ ..., the better the range for each colormap will be pinpointed. However, if for instance I set n1 = 1024, n2 = 1024 in the code snippet above the colorbar will be faulty:
Questions: 1) Is this a bug, or a limitation implemented on purpose to fulfill another constraint?
2) Can the maximal sum of values n1 + n2 + ... be determined?


Yes, mine also looks like the top one. The caxis stuff is just to centre 0 which was something mentioned in the original question as having the colourmaps join at an essentially arbitrary value is misleading.
@David Goodmanson: No, I haven't figured out why it sometimes looks as in the bottom figure. The maximum value that works sometimes differ for a single computer, depending on change in some parameters I have not pinpointed yet. If I figure out I will post here.
Thanks Hannes. I and several other folks will be interested to know what is going on once you find out.

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