Subsetting a row of a matrix according to conditions in another row

I have a matrix in which the first row is some kind of index (let's say ranging from 1 to 50) and the second row is some varible y, like this:

t = repmat(1:50,1,50)

M = [ t ; y ]

I want to extract those entries of y which correspond to a given subset of the indexes, like

y([such that the corresponding t entry = to some subset of 1:50])

Is there some efficient way to do it avoiding loops or heavy demanding scripts?

Thank you

Answer 1

[Matt J]

y( ismember(t, subset) );