MATLAB Answers

John
2

Making two different color maps in 2014b

Asked by John
on 18 Nov 2014
Latest activity Commented on by Steven Lord
on 23 Sep 2016
I'm trying to figure out how to use two different color maps in 2014b and use multiple color bars. Specifically I want to plot some image data and on top of that plot a set of contours.
Basically in the past I used freezecolors and cbfreeze. The same method behind freezecolors still works, changing the CData of your image to RGB values, but the colorbar is still a problem. CBfreeze doesn't seem to work any more because the colorbar objects are no long structs and now are specific objects.
I want to have separate colorbars for both the image data and contours but I can't seem to figure out the issue with the colorbars.
Thanks,
John

  3 Comments

In R2014b MATLAB there is a colormap per axes, not just per figure. This solves lot of problems from the past. Since you are still using freezecolors to get two colormaps in the same axes, that is still fine.
The real question is getting two colorbars for the same axes, correct?
Can you post a typical firgure from before?
I have the same question/problem. I am attaching a figure of what I could do before 2014b using freezeColors and cbfreeze. However, cbfreeze does not seem to work in 2014b. Thank you.
Adam
on 19 Nov 2014
Wow, I'd never noticed R2014b snuck in that change. It's something I've wanted for quite a while, but must have missed in the changes listings!

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5 Answers

Answer by Sean de Wolski
on 18 Nov 2014
Edited by Sean de Wolski
on 18 Nov 2014
 Accepted Answer

You can still use the freezecolors approach or one like I use in my meshCanopy function (same idea). You'll need to set the 'Limits' property of the colorbar to the range you want (and perhaps the tick/ticklabel etc.). For example:
I = imread('cameraman.tif');
n = 64;
meshCanopy(I,stdfilt(I),parula(n),80);
h = colorbar;
%%Now compare
h.Limits = [256 256+n];

  0 Comments

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Answer by Nash Chu
on 23 Sep 2016
Edited by Nash Chu
on 23 Sep 2016

Actually you just need to add 'gca' when you define your colormap. like this:
figure
subplot(2,1,1)
pcolor(x,y,pxy);shading interp;
colormap(gca,jet);
colorbar;
subplot(2,1,2)
pcolor(x,y,pxy);shading interp;
colormap(gca,autumn);
colorbar;

  1 Comment

I recommend avoiding using gca in your program files. When experimenting in the Command Window it's okay, but inside a function (and especially inside a GUI) it's too easy for the current axes to change without you realizing it. [As one example you create an axes intending to manipulate it using gca but before you can your user gets a little bored and clicks on a different axes.]
Instead, call subplot with an output argument (which will be the handle of the subplot axes) and pass that handle into colormap.
h = subplot(2, 1, 1);
% stuff
colormap(h, jet);

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Answer by Jorge Ramirez on 19 Nov 2014

Thank you, Sean. However, the problem is how to add two different colorbars corresponding to the two different colormaps. Your example shows only one colorbar. I am attaching an example graph of what I mean. I produced the attached graph with Matlab 2013b using freezecolors and cbfreeze. However, as I said, cbfreeze does not work anylonger on Matlab 2014b.
Thank you.
Jorge

  2 Comments

In that case just call colorbar twice and change the position as necessary:
I = imread('cameraman.tif');
meshCanopy(I,stdfilt(I),parula(64),80);
ax = gca;
h = colorbar('peer',ax);
h.Limits = [1 256];
h.Ticks = [];
h.Position(1) = h.Position(1)-0.1;
h = colorbar('peer',ax);
h.Limits = [256 256+64];
h.Ticks = [];
Hi Sean,
I think you got it, thanks for the help! The only thing I'm going to have to watch out for is if the two data sources here are in the same range. It looks like you get around that by adding an offset to the data in the manifold right? I believe you can work around this by changing the labeling on the colorbar. I'll post a piece of example code if I get it working to show what I'm talking about.

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Answer by Raul
on 17 Feb 2015

Still isn't clear how to use two different colormaps. How do you change the colormap?

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Answer by Chad Greene
on 16 Aug 2015

I made a solution to this for a problem I was working on. It's called newcolorbar.

  1 Comment

thanks for your suggest

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