Use randperm in a matrix in MATLAB

I have a matrix called "featureMatrix". using size(featureMatrix) the result is: 11843 720. I want to shuffle the content of this matrix using randperm. First I choose the seed using rng(1). Then I use randperm: featureMatrixRnd = featureMatrix(randperm(length(featureMatrix))');. But it didn't work good. In fact if i write size(featureMatrixRnd) I obtain 11843 1, instead of 11843 720. why?