Edited "Again I am Asking About Random sampling."

Dear Walter,

I have a matrix A, size ( 494020 x 41) samples , this matrix contain randomly distributed samples of four class , like DOS, Prob, U2R, R2L, further these classes have sub class and these subclasses samples distributed in Matrix A, I need only Dos class related samples, the Dos class have sub class is (Back, land ,Neptune ,pod, smurf, teardrop) Basically these are labels related to the samples that I want like, I need 40 sample of Back. I need 50 sample of land. Need 100 sample of Neptune. Need 100 sample of teardrop. Need 500 samples of smurf. Need 100 samples of Pod. How I can get these sample randomly, I need 391458 samples of all subclass.

[Walter Roberson]

Duplicates http://uk.mathworks.com/matlabcentral/answers/254393-pleasae-help-me-random-sampling