How do I change the colors in a legend on a bar plot when I change the colors of the bars?
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I am having some problems with adapting a legend to a bar plot.
I have changed the colors of the bars, but when creating the legend I just have the option of putting one. When I put more entries I get the message
'Ignoring extra legend entries'
I have found in some other posts a way of putting more extra legends, but the problem is that they all have the same color and I have not found the way to change that!
Here is an example of what I mean:
data = rand(1,12);
index = ones(1,length(data));
mycolor=[0 1 0;0 0 1;1 0 0;0 1 1];
In this way I have the bars in the different colors I want. Now I would like to have a legend with four entries specifying the four different colors and the legend (for example) 'a','b','c','d'...
What I have found in other posts is:
But I just get the same color in all the entries!
Walter Roberson on 20 Jan 2011
You cannot do what you want using legend when you use bar() with a row or column vector. Internals of how legends are handled are described in MATLAB documentation.
We can see through examination of your code that only a single barseries object is being produced and it will have only a single patch object as its child. The documentation referenced earlier shows that only a single legend slot is available for this situation. You can get multiple lines for the legend but there is not enough control information available to assign them different colors.
What you should be doing instead is using multiple bar() calls, one per group. You can specify the y values to be associated with the entries so that they will all appear on one graph, and you can legend() the groupings.
More Answers (2)
Doug Hull on 20 Jan 2011
The ability to change the color in each bar of a plot is not built into MATLAB.
As a workaround, you can return handles to the patch objects that define the bars, and change their colors using Handle Graphics. If you are using MATLAB 7.0 (R14) or later, you will need to use the 'v6' option to the BAR function to obtain handles to patch objects. In earlier versions, this is not necessary.
Y=[ 1 2 3 ; 4 5 6 ; 3 4 5];
h = bar('v6',Y);
set(h(1),'facecolor','red') % use color name
set(h(2),'facecolor',[0 1 0]) % or use RGB triple
set(h(3),'facecolor','b') % or use a color defined in the help for PLOT
Note: This would not have any effect on the legend colors. Hence you would need to change the legend colors similarly. You can get the handle of the legend and look for the children.
Haris on 6 Apr 2012
I have found a way to display the bars with different colors. Let say that you have 4 measurements a, b, c and d that you want to display with different color each:
a = 1;
b = 2;
c = 3;
d = 4;
if you represent these values as
a2 = [ a 0 0 0 ];
b2 = [ 0 b 0 0 ];
c2 = [ 0 0 c 0 ];
d2 = [ 0 0 0 d ];
then you can display them with different colors:
legend('a', 'b', 'c', 'd');