If I understood correctly, you need weighted sampling. Try 'prob'
argument from 'sample'. For your example:
n - 10
ntype - rbinom(n, 1, 0.5)
myProbs - rep(1/10, 10) # equally likely
myProbs[ which(ntype == 0)] - 0.75/7 # Divide so the sum will be 1.0
myProbs[ which(ntype == 1)] - 0.25/3
sample(ntype,3, prob=myProbs)
On 5 March 2014 15:20, Thomas thomas.ches...@nottingham.ac.uk wrote:
I have a matrix where each entry represents a data subject's type, 1 or 0:
n - 10
ntype - rbinom(n, 1, 0.5)
and I'd like to sample say 3 subjects from ntype where those subjects who
are Type 1 are selected with probability say 0.75, and Type 0 with (1-0.75).
(So the sample would produce a list with three indices each referring to a
position within ntype.)
Can anyone suggest a way to do this please?
Thank you,
Thomas Chesney
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