Box Plot for large groups of Measurements

I've got basically three large groups of measurements and im trying to generate a BoxPlot with 4 Boxes. One box for each group and the last one for all groups joined.

I've tried with this code

    A = rand(1417725,1)
    B = rand(2236508,1)
    C = rand(3100641,1)
    D = [A;B;C]

    X= [A;B;C,D]

    group = [repmat({'a'},1417725,1); repmat({'b'},2236508,1); repmat({'c'},3100641,1); repmat({'d'},6754874,1)];

    boxplot(X,group)

but at the end i get " Out of memory" and i can't get the plot.

do you have any idea to solve this problem??

Thank you!