MATLAB boxplot of high dimensional vectors with different lengths - matlab

Question

I have been looking for a way to use boxplot for different length vectors. thanx for stackoverflow helpers, they give this solution:
A = randn(10, 1); B = randn(12, 1); C = randn(4, 1);
g = [repmat(1, [10, 1]) ; repmat(2, [12, 1]); repmat(3, [4, 1])];
figure; boxplot([A; B; C], g);
unfortunately, my data contains over 100 vectors with different lengths, I wonder if it can be done without repeating the repmat for over 100 times.

Answer 1

As long as your vectors have different lengths, store it in a cell array.
There are plenty was of doing it, here are 3 examples
1) "Naive" for loop
g = [];
vars_cell = {A, B, C, ....};
for it = 1 : length(vars_cell)
g = [g; repmat(it,size(vars_cell{it}))];
end
This way of doing it works but is very slow with big quantites of vectors or big vectors! It comes from the fact that you are re-defining g at each iteration, changing its size each time.
2) Not-naive for loop
vars_cell = {A, B, C, ....};
%find the sum of the length of all the vectors
total_l = sum(cellfun(#(x) length(x),vars_cell));
g = zeros(total_l,1);
acc = 1;
for it = 1 : length(vars_cell)
l = size(vars_cell{it});
g(acc:acc+l-1) = repmat(it,l);
acc = acc+l;
end
This method will be much faster than the 1st one because it defines g only once
3) The "one-liner"
vars_cell = {A, B, C, ....};
g = cell2mat(arrayfun(#(it) repmat(it, size(vars_cell{it})),1:length(vars_cell),'UniformOutput',0)');
This is qute equivalent to the 2nd solution, but if you like one line answers this is what you are looking for!