In MATLAB, I want to convert a vector of text elements into numbers in order to plot them.

Question

In MATLAB, I want to convert a vector of text elements into numbers in order to plot them.

For example, say I have the following data

team = [blue g         


        

Answer 1

I'm assuming the text elements are in a cell array, like so:

team = {'blue', 'green', 'blue', 'yellow', 'green', 'blue'};

It isn't possible to make a normal vector / array with multiple strings, as this would basically create a single string that concatenates all of these strings together. You'd have to split them up into a cell array... now onto your question.

You can use the third output parameter of unique. This output basically assigns each unique element in an array or cell array a unique ID number. In this case, if you did:

[~,~,id] = unique(team)

... we would get:

id =

 1
 2
 1
 3
 2
 1

... which is exactly what you want!

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As a bonus for you, we can easily plot this, changing the x axis to each of those labels. In other words:

score = [20 45 74 10 11 42].'; %// Transpose as id is transposed '
plot(id, score, 'b.', 'MarkerSize', 16);  % // Plot the points
                                          % // Marker size is 16
set(gca, 'XTick', 1:3); %// Only set three ticks to 
                        %// be visible as there are 3 IDs
xlim([0 4]); %// Make the x-axis bigger
set(gca, 'XTickLabel', ...
   {'blue', 'green', 'yellow'}); %// Change the numeric labels to text
grid; %// Put a grid on

... and this is the figure I get: