How to find 'within group correlation'?

I am new to matlab and I'm working on a problem with training data X and target data t. The target t is either 1 or 0 denoting which class the rows of X belong to. X is a 179x2 matrix, and I'm supposed to find the "within group correlation" between two variables x1 and x2 for each class. Can anyone explain how to do this? The professor's notes don't mention this at all

Answer 1

[Jeff Miller]

I would guess the idea is this:

grp0 = t == 0;
grp1 = t == 1;

corr(x(grp0,:))
corr(x(grp1,:))