Hi Ahmed,
From the example on the documentation, when you say
c = mat2cell(x, [10, 20, 30], [25, 25])
you should expect 'c' to have 6 (3*2) effective cell arrays. (3*2) comes from the size of the last two arguments in the above command. [10, 20, 30] specifies the number of rows in each resulting cell arrays and [25, 25] specifies columns. Now in your case you'd like to have 4 cell arrays but all of them have same number of columns. So the last two parameters should be of size 4 and 1.
X = rand(7,3)
C = mat2cell(X, [2 2 2 1], 3);
celldisp(C)
Now the last two parameters specify how you wanna distribute rows and columns respectively. Hope this was helpful. (the pictorial representation from the doc page helps you visualize the distribution quite easily.)
KL.
