How to access the minor of a matrix.

If I have an n x n matrix, is there a way to access a smaller part of the matrix (thus yielding a smaller matrix) with arbitrary size? For instance, I have a randomly generated 32x32 matrix and I would like to access the 16x16 block in the lower right. I suppose I could simply access the entries I want but that seems inefficient, particularly as my matrix sizes increase.

[Matt J]

What is the difference between this:

is there a way to access a smaller part of the matrix (thus yielding a smaller matrix) with arbitrary size

and accessing the entries:

I suppose I could simply access the entries I want but that seems inefficient, particularly as my matrix sizes increase.

[Jan]

What exactly seems inefficient?

[Hayashi]

There isn't a difference. I can construct the minor by accessing the entries. I was wondering if I could simply specify the minor I want and MATLAB could create it.

Answer 1

[Iain]

 big = randn(1000,1000,4);

 small = big(n:n+m,o:o+p,q:q+r);

small is an m+1 x p+1 x r+1 matrix, which was taken starting at (n,o,q) of the big one...

It works on whatever number of dimensions you need.

[Matt J]

@Hayashi

This doesn't seem different from "accessing the entries". The expression

 small = big(n:n+m,o:o+p,q:q+r);

does access entries from "big".