[R] means and variances of several groups in the matrix

From: kathie <kathryn.lord2000_at_gmail.com>
Date: Mon, 21 Apr 2008 00:03:30 -0700 (PDT)

Dear R users,

I have 32 observations in data x. After sorting this, I want to compute means and variances of 3 groups divided by "nr".

Actually, the number of groups is flexible. Any suggestion will be greatly appreciated.

Kathryn Lord



x=rnorm(32)
y=sort(x)

nr=matrix(c(12,11,10,10,10,11),2,3)
> nr

     [,1] [,2] [,3]
[1,] 12 10 10 -> sum=32
[2,] 11 10 11 -> sum=32

For the 1st row in "nr", index of y = (1,..,12, 13,...,23, 24,...32)

I want to compute means and variances for 3 groups

(1st group is 1 through 12; 2nd group is 13-23; 3rd group is 24-32)

For the 2nd row in "nr", index of y = (1,..,11, 12,...,22, 23,...32)

also, I want to compute means and variances for 3 groups

(1st group is 1 through 11; 2nd group is 12-22; 3rd group is 23-32)

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