how to do this in a for loop in Matlab

I have a 3-dimensial matrix W(160,170,18) and wanna to compute the difference between each to sucessive matrices inside W. for example diff1 = W(:,:,1) - W(:,:,2) and diff2 = W(:,:,2) - W(:,:,3), etc ...

Next I want to select some special parts of the resulting matrices, For example:

NewDiff1 = [diff1(20:50,110:140);diff1(60:90,110:140)];

and the same thing for the other matrices. finally I want to compute the mean of each matrix and the error as follow:

mean1 = mean(mean(NewDiff1)); er1 = 0.1-abs(mean1);

I successeded to do this for each matrix alone, but prefer to do all at once in a for loop. Can you please help me to do it.

Answer 1

[Andrei Bobrov]

dff = diff(W,1,3)
a = dff([20:50,60:90],110:140,:)
meanN = mean(reshape(a,[],size(a,3)));
erN = .1 - abs(meanN);

[Daniel Shub]

You beat me. Nice use of reshape over mean(mean()).

[Ali]

very smart solution. thank you very much

Answer 2

[Daniel Shub]

I am not sure if this is really what you want ...

First create some dummy data

x = randn(160,170,18);

You can create all your "diff" matrices with the diff function.

y = diff(x, 1, 3);

Since they are all 1 matrix, calculating the mean and error is now easy

mu = squeeze(mean(mean(y([20:50, 60:90], 110:140, :))));
er = 0.1-abs(mu);