Pleasae help me (Random Sampling)

Dear Sir,

I am Using KDD99 data set. having four class DOS, Prob, U2R and R2L, I need a random sample of DOS with sub attacks of DOS like ( Back, land, neptune, pod, smurf, teardrop) from Kdd99.

I need 39,1460 random sample of DOS with sub attacks, can any body help me, I need a code.

[Merged from duplicate question]

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]

Given your matrix A, how can you tell whether a given row of it belongs to a particular class or sub-class?

[Rehan Ali]

yes Sir, that is a question ? so for that i have convert my labels to Numeric like

   Back= 1   , land = 7, neptune = 10, pod= 15, smurf = 19 , teardrop = 21 ,

these are the label that belong to each class. may be if we know the indices of these label then we can get the samples very easily from matrix A , but how?

[Walter Roberson]

Which column of matrix A indicates which of the 4 classes DOS, Prob, U2R or R2L the row belongs to? For a row that belongs to DOS, which column of matrix A indicates which of the types of DOS it is?