matlab colorbar for lineplot colored by value

4
votes

I have 2d line plot in matlab where each line is colored according to a value. I would like to add a colorbar showing the color that corresponds to these values.

I got a solution to plot the lines according to the value I want, however I can not figure out to get the colorbar correctly. I have been searching on this but I am stuck.

  1. Define an RGB color matrix COL. (N x 3 low red to dark matrix corresponding to equally spaced values 0:1).
  2. Sort the data according to their z value.
  3. Interpolate the COL matrix to get values for all z values, giving the TRUECOL matrix for the lines.
  4. Set the axiscolor-ordering to the TRUECOL matrix and plot the data.

minimalistic example: 

% Generate 10 lines of 10 points
x = normrnd(0,1,10,10);
% The corresponding values are 
% Note that these do not have to linearly spaced in real code
z = [0,0.05,0.1,0.11,0.12,0.2,0.4,0.45,0.8,0.9];
% Define colormatrix
COL = [0.996078431372549 0.878431372549020 0.823529411764706;...
   0.937254901960784 0.231372549019608 0.172549019607843;...
   0.403921568627451 0 0.0509803921568627];
% Interpolate the COL matrix to get colors for the data
TRUECOL = interp1(linspace(0,1,3),COL,z,'pchip');
% Set the axis coloring qnd plot the data
set(gcf,'DefaultAxesColorOrder',TRUECOL);
plot(x);
colormap(TRUECOL);
colorbar

I then change the colormap and plot the colobar, however the colors in the colorbar to not correspond to the values z. Is there a way of telling matlab which color corresponds to which value? Looking at the colorbar editor I see that CData must have something to do with it, but I cant find a way to specify that CData should be z.

1
matlabplotcolorbarline-plot
Can you complete your example by adding the change of colormap and plotting of colorbar? – Trilarion
The colorbar colors and the line colors look roughly similar. What do you mean by "not correspond"? – Trilarion
I changed the z values to make it more clear. To colorbar ranges from 1 to 11 (This can be changed with CLim property). if you open the colobar editor you can see that the colors in the colorbar are linearly mapped in steps of 0.1. I would like to have to colorbar show the actual z values corresponding to the colors in the TRUECOL matrix. Thus the result in the interpolation. – MrOperator
Another item in the giant List of Simple Things That MATLAB Cannot Do Automatically" :-/ – Flyto

1 Answers

2
votes

My understanding is that you want the labels on the colorbar to go from 0 to 1, not 0 to 11. To fix this, use this caxis command. To get finer gradations of colors in the colorbar, you need to more finely interpolate the colormap. Try this:

colormap(interp1(linspace(0,1,size(COL,1)), COL, linspace(0,1,100)));
caxis([0,1]);
colorbar

enter image description here