The title is perhaps not very clear...
I have a 3 vectors X, Y and Z of same dimension N.
I have also 2 intervals vectors containing the limit of each interval (wich are not necessary equidistant) of X and Y values: int_X (dimension i_X) and int_Y (dimension i_Y).
I want to calculate the mean value of Z for each interval of both int_X and int_Y (each "square" of the (int_X,int_Y) plane), and put the results in a matrix of dimension (i_X,i_Y).
Of course, I can do it with 2 "for" loops, but I would like to find a more elegant method without for loops.