Matlab Code – Change color of data points for each subject/group

This came about because I wanted to make a bar graph from a data set. In these data, each of my seven subjects contributed multiple data points. I wanted each bar that corresponded to a subject to be a unique color. I couldn’t find it anywhere online so here is a routine to accomplish it with either subjects as a cell array or numerical array. Note: You must have Matlab 2018a or greater. Otherwise you will get a CData error.

%% Subjects in a cell array as strings 
data = [1 2 3 4 5 6 7 8 9]; % data should be a vector of the data you want to plot
subjects = {'A' 'B' 'C' 'A' 'B' 'C' 'A' 'B' 'C'}; % subject index should be a vector the same size as data which indicates the subject belonging to each element in your data vector
uniqueSubjects = unique(subjects);
cmap = colormap(hsv(length(uniqueSubjects))); % total subjects is the total number of subjects you have
                                     % I used the hsv colormap; use whichever one suits your needs 
b = bar(data,1,'FaceColor','flat');  % plot bar graph
    for i = 1:length(uniqueSubjects)  % for every subject
        currentSubject= uniqueSubjects{i}; % get the name of the current subject
        indexSubject = strfind(subjects,currentSubject);  % find where they are 
        index = find(not(cellfun('isempty',indexSubject )));  % get their index location
        for j = 1:length(index) % go through whole index
            b.CData(index(j),:) = cmap(i,:); % set each bar to the color corresponding to current subject
        end
    end

%% Subject names as numerical array
data = [1 2 3 4 5 6 7 8 9]; % data should be a vector of the data you want to plot
subjects = [1 2 3 1 2 3 1 2 3]; % subject index should be a vector the same size as data which indicates the subject belonging to each element in your data vector
uniqueSubjects = unique(subjects);
cmap = colormap(gray(length(uniqueSubjects ))); % total subjects is the total number of subjects you have
                                     % I used the gray colormap; use whichever one suits your needs 
b = bar(data,1,'FaceColor','flat');  % plot bar graph
    for i = 1:length(uniqueSubjects)  % for every subject
        currentSubject= uniqueSubjects(i); % get the name of the current subject
        index = find(subjects == currentSubject);  % find where they are 
        for j = 1:length(index) % go through whole index
            b.CData(index(j),:) = cmap(i,:); % set each bar to the color corresponding to current subject
        end
    end