Hi guys !! First of all, I'd like to say that this group is really excellent, atleast we people who have questions regarding Matlab can communicate with Other people. you all guys great ...... Now here is a question which I have, I know if I want to filter a 2d-matrix with butterworth filter, I can do T=randn(50); [B,A]=butter(8,0.4); TT=filter(B,A,T); TT=filter(B,A,TT'); but I am trying to filter a 3-dimensional random matrix, by using butterworth filter, so please help with this code. here is what i did but its not working T=randn(50,50,50); [B,A]=butter(6,0.1); TT=filter(B,A,TT); Can any body know how to use for loop and split 3d matrix into 2d slices and then use the same technique which I did in 2d case OR perhaps any other filter I should use which performs a low pass filtering for my 3d matrix. Cheers Simon.