how to balance data set by oversampling?

Hello. I have a matrix of sleep EEG signal. Each row of the matrix belongs to an sleep stage ( There are 5 sleep stages including:W, N1, N2, N3, REM). I want to balance my matrix like this: 1) Find which sleep stage has the most samples. 2) Duplicate the minority sleep stages in the matrix such that all sleep stages have the same number of samples (i.e., oversampling). Can anyone help me do this task in MATLAB?

Regards.