Assigning matrix rows with particular indices

I am porting some code from Matlab to Armadillo and am stuck at a simple step. I am finding all the indices of a vector res on the basis of a condition and then want to store all the rows of a matrix Pts corresponding to the condition.

So what it is in matlab

ifAny = find(res < lim);
Pts = Pts(ifAny,:);

In Armadillo -

arma::uvec ifAny = arma::find(res < lim);
// elem gives only the single column
// Pts = Pts.elem(ifAny);