MATLAB: How to see the changes in the image color when I manually edit the bounds in the COLORMAPEDITOR in MATLAB (R2013a)

cdatamappingcolormapeditordirectMATLABscaled

When I change the Min and Max values of the Color Data in the COLORMAPEDITOR, I do not see any changes in my figure. I have a line object on my figure. Could you please explain why is this so?

Best Answer

The ability to change the Color Data Mapping for line is not possible, as of MATLAB (R2013a). However, for surface, image and patch objects, you can do so by changing the default Color Data Mapping from 'direct' to 'scaled'.

Here is an example that shows that:

clc
close all
clear all
load flujet
image(X)
colormap(jet)
set(gcf,'windowstyle','docked')
hc  = get(gcf,'children');
hcc = get(hc ,'children');
set(hcc,'cdatamapping','scaled')
% Launch the colormap editor
Colormapeditor

For this case, the default color data limits are 1 and 64. Now, in the COLORMAPEDITOR, you can manually change the values of Color Data min and Color Data max to -10 and 20, for example and you will see that the figure color is updated.

Related Solutions

MATLAB: How to set the colorbar to have a limited number of colors

For MATLAB versions R2014b and later:

As of MATLAB R2014b, you can accomplish this with the 'colormap' function. You can use the 'colormap' function to customize the range of colors that gets displayed. You can create a completely custom colormap by specifying each RGB value:

map = [0, 0, 0.3;
  0, 0, 0.4;
  0, 0, 0.5;
  0, 0, 0.6;
  0, 0, 0.8;
  0, 0, 1.0];
colormap(map)

Or if you would like a starting point for creating the values in 'map', you can use values from one of the built-in colormaps:

>> map = parula(64)

For MATLAB versions R2014a and earlier:

The ability to set the number of colors in a colorbar is not directly available in MATLAB.

However, this is possible by changing the 'CData' property of the image that resides in the COLORBAR axes, as shown in the example below:

mx = peaks(100);
numberOfColors = 5;
% This value will be used in the code below to set the number of colors as desired
nc = numberOfColors-1;
% Use this syntax of contourf to select number of contours
[c,h, cf] =contourf(mx,nc);
cb = colorbar;
% Find the image inside the colorbar object,
% then find the limits of the data to set colorbar axes
i = findobj(cb,'type','image');
minVal = min(mx(:));
maxVal = max(mx(:));
% Set the colorbar's CData to the desired number of intervals
set(i,'cdata',[0:64/nc:64]','YData',[minVal maxVal]);

Finally, set the tick marks of the colorbar:

% Option 1: Set the colorbar ticks to sit in the center of the color bins
set(cb,'yLim',[minVal maxVal],'ytick',[minVal:(maxVal-minVal)/(nc):maxVal]');   
% Option 2: Set the ticks to sit both at the centers and at the edges of the color bins
%set(cb,'yLim',[minVal maxVal],'ytick',[minVal:(maxVal-minVal)/(2*nc):maxVal]');

You can refer to the documentation for more details and examples:

https://www.mathworks.com/help/matlab/ref/colormap.html

MATLAB: How to create a legend with multiple outputs

The recommended workflow for creating a legend entry that does not match an existing plot in your data is to create a separate entry in your plot with either empty or NaN data. This will render the new entry invisible, but it will still show up in the legend. Then you can adjust the properties of that new object to make the legend entry appear as you require.

Below is the example on how you can do it. Please run the below code in command line and also in App Designer.

hFig = figure;
hAx = axes(hFig);
hScatter= scatter(hAx,1:10,1:10,'b');
hold on;
hObj(1)=plot(NaN,'b','Marker','o','LineWidth',2,'MarkerEdgeColor','k','MarkerFaceColor','b','LineStyle','none','MarkerSize',10);
hObj(2)=plot(NaN,'b','Marker','o','LineWidth',2,'MarkerEdgeColor','k','MarkerFaceColor','b','LineStyle','none','MarkerSize',12);
lg=legend(hObj,{'My Data 1','My Data 2'});

Best Answer

Related Solutions

MATLAB: How to set the colorbar to have a limited number of colors

MATLAB: How to create a legend with multiple outputs

Related Question