How can we implement a for loop for finding maximum of three gradient matrices?

[Rx, Ry] = imgradientxy(r); [Rmag, Rdir] = imgradient(Rx, Ry); [Gx, Gy] = imgradientxy(g); [Gmag, Gdir] = imgradient(Gx, Gy); [Bx, By] = imgradientxy(b); [Bmag, Bdir] = imgradient(Bx, By);

I have to find max of these three matrices B G and R