MATLAB: How to color the bars of the stacked bar chart based on another variable

barcdataclimcolorcolorbarcolormapcolorscaleMATLABstacked

I have created a horizontal bar chart with one stack. I have an array "duration" that describes how wide each bar should be. When I plot the stacked bar chart as below, the colors are assigned automatically:

>> duration = [1 2 3 4 5 4 3 2 1];
>> b = barh(0,duration,'stacked');

However, I want to assign the colors based on another variable, "satisfaction", which is an array of doubles.

>> satisfaction = [12 22 34 42 51 63 77 84 95];

How can I assign colors to my bars based on this array of doubles?

Best Answer

A possible solution is to map your "satisfaction" data onto a colormap, then assign a color to each bar in your chart based on that colormap:

https://www.mathworks.com/help/matlab/ref/bar.html#d117e81991

To do so, first set the "FaceColor" of the bars to "flat":

>> ax = axes;
>> b = barh(ax,0,duration,'stacked','FaceColor','flat');

Then, change the axes color limits to match those of your "satisfaction" data:

>> ax.CLim = [min(satisfaction) max(satisfaction)];

To label the colorbar and the x-axis of the plot, we write:

>> c = colorbar;
>> c.Label.String = 'Satisfaction';
>> xlabel('Duration');

Once the colormap is setup, you can assign each bar's "CData" to the corresponding "satisfaction" value:

for i = 1:length(duration)
  b(i).CData = satisfaction(i);
end

This will produce the color mapping you expect. You can also change the scale of the colormap from linear to logarithmic by using the "ColorScale" property on the axes:

https://www.mathworks.com/help/matlab/ref/matlab.graphics.axis.axes-properties.html#budumk7-ColorScale

For example,

>> ax.ColorScale = "log";

I have attached a file to this post, combining all the steps described above into a single script.

Related Solutions

MATLAB: Displaying names of multiple variables in a plot

Let us assume that you have following variables created in your workspace:

>> v1 = rand(10,1);

>> v2 = rand(10,1)+1;

>> v3 = rand(10,1)+2;

>> v4 = rand(10,1)+3;

>> v5 = rand(10,1)+4;

>> v6 = rand(10,1)+5;

>> v7 = rand(10,1)+6;

>> v8 = rand(10,1)+7;

>> v9 = rand(10,1)+8;

1. You can concatenate all the variables into a matrix and then you can plot them as you iterate over matrix of variables using "for" loop with "hold on" command. To accomplish that you can execute following code:

>> variables = [v1,v2,v3,v4,v5,v6,v7,v8,v9]; % This creates (10-by-9) matrix containing variables as individual columns. All the variables should have same number of values else MATLAB will throw an error.

>> for i = 1:9

>> plot(dates, variables(:,i)); % Variables are plotted column by column.

>> hold on;

>> end

>> varNames = {'y = IEI','y = IEF','y = SHY','y = TLH','y = TLT','y = TIP','y = AGZ','y = CIU','y = HYG'}; % Create a cell array of strings for legend

>> legend(varNames, 'Location', 'SouthWest'); % Provide the cell array as an argument to "legend" function. Number of entries in cell array should be same as number of variables.

>> xlabel('Date');

>> ylabel('Normalized Price');

>> title('Normalized Asset Prices and Benchmark');

>> datetick('x');

>> grid on;

>> hold off;

2. You can concatenate all the variables into a matrix and provide that matrix as input to the plot function which will plot the data for you. You do not have to use "hold on" command in this approach. To accomplish this you can execute:

>> plot(dates,variables); % Variables are plotted column by column.