[R] Sample without replacement
Hello, I have a simple problem (checked the archives and the appropriate
help pages, to no avail). I want to creat a vector that is length(2000).
The vector is to consist of two strings( std and dev) with 1760 stds
and 240 devs. Furthermore, for each element of the vector, i want the
selection of one of the strings to be approx. random. The end result will
be a vector with the following proportions: .12 dev and .88 std.
My solution, below, almost works, but i don't get the exact desired
proportions:
sample.from.vector - c(rep(std,1760),rep(dev,240))
make.vector - rep(99,2000)
for (i in 1:2000){
make.vector[i] - sample(sample.from.vector,1,replace=F)
}
As I understand the above code (which is not very well, obviously), each
iteration assigns one element from the sample.from.vector to the current
make.vector element; the element choosen from sample.from.vector is
tagged so that i is not selected again. However, after the loop,
make.vector contains, for example, 1758 stds and 242 devs. Each
iteration results in a different proportion of stds and devs (although
close to the desired, not right on).
Any help would be greatly apprecitated.
-Mark Orr
Mark G. Orr
Postdoctoral Research Fellow
Dept. of Neuroscience
RM 825 Kennedy Center
Albert Einstein College of Medicine
Bronx, NY 10461
718-430-2610
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Re: [R] Sample without replacement
Mark G Orr [EMAIL PROTECTED] writes:
Hello, I have a simple problem (checked the archives and the
appropriate help pages, to no avail). I want to creat a vector that
is length(2000). The vector is to consist of two strings( std and
dev) with 1760 stds and 240 devs. Furthermore, for each element
of the vector, i want the selection of one of the strings to be
approx. random. The end result will be a vector with the following
proportions: .12 dev and .88 std. My solution, below, almost
works, but i don't get the exact desired proportions:
sample.from.vector - c(rep(std,1760),rep(dev,240))
make.vector - rep(99,2000)
for (i in 1:2000){
make.vector[i] - sample(sample.from.vector,1,replace=F)
}
As I understand the above code (which is not very well, obviously),
each iteration assigns one element from the sample.from.vector to the
current make.vector element; the element choosen from
sample.from.vector is tagged so that i is not selected again.
However, after the loop, make.vector contains, for example, 1758 stds
and 242 devs. Each iteration results in a different proportion of
stds and devs (although close to the desired, not right on).
Any help would be greatly apprecitated.
It's staring you right in the face:
make.vector - sample(sample.from.vector)
--
O__ Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907
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