[R] means and variances of several groups in the matrix
kathie
kathryn.lord2000 at gmail.com
Mon Apr 21 09:03:30 CEST 2008
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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