What does this mean in MATLAB?

I have came about a MATLAB code like the following:

xyz = imfilter(A,B);
xyz_subsample = xyz(1:2:size(xyz, 1), 1:2:size(xyz, 2));

The code is related to subsampling. But, what does the second line mean?

Thanks.

[Jan]

@med-sweng: Your questions have a very low acceptance rate. This usually means, that there is a problem in the way you ask. In long term, this can discourage contributors to spend the time for answering your questions. So it is in your own interest to clarify your questions until they can be answered successfully, and accept this answer then.

Answer 1

[Jan]

It crops every 2nd line and column out of the matrix xyz.

Simply try it:

xyz  = randi(99, 10, 10)
xyzS = xyz(1:2:size(xyz, 1), 1:2:size(xyz, 2))

Answer 2

[the cyclist]

Suppose xyz is a 256x512 matrix. Then

size(xyz,1)

is 256 and

size(xyz,2)

is 512.

The code

1:2:size(xyz,1)

is a vector counting by 2's:

[1 3 5 7 ... 255]

and likewise for the second dimension.

So, the whole code is subsampling by only selecting every 2nd element of both the x and y dimensions.

[med-sweng]

Thanks for your nice answer. So, the code will choose the following values from "x" for instance: 1, 3, 5, ..., 255, right?

[the cyclist]

As Jan also describes, your code keeps rows 1,3,5,... and columns 1,3,5 ... .