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Message-ID: <AA89BFA18D20A8469B6E05BBC55E4471713F3034@EXCH10-MBX-06.home.ku.edu>
Date: 2011-11-05T00:38:20Z
From: Md Desa, Zairul Nor Deana Binti
Subject: set seed for random draws

Hello, all!
I need help on these two problems:

1) If I want to randomly draw numbers from standard normal (or other distributions) in loops e.g.:
 ty=0; ks=0
for (i in 1:5) {
        set.seed(14537+i)
        k<-rnorm(1)
        ks[i]<-.3*k+.9
        if (ty==0) {
            while ((ks<.2)||(ks>3)) {
            #set.seed(13237+i*100)
            k<-rnorm(1)
            ks[i]-.3*k+.9 }
        }
     }
....
....
....
     }

Question: Here I draw initial a, then if the drawn initial a satisfied 2 conditions I redraw a. I set.seed(13237) in the first draw of a, should I set.seed() in the redraw part?

2) I also have more loops after this i loop that also draw from normal(0,1). I want to randomly draws from normal(0,1) for loop j (inside loop j I draw another random numbers from N(0,1))
My question: Should I or shouldn't I set seed again and again for each loop? Why or why not.

I guess this problem concerned about setting seed as I want to have different number for each i.

Thanks!

Deana