I believe this does what you want:
m[-sample(which(m[,1]<8 & m[,2]>12),2),]
Analysis:
Get a boolean vector of rows fitting criteria:
m[,1]<8 & m[,2]>12
What are their indexes?
which(...)
Choose two among those indexes:
sample(...,2)
Choose all except the selected rows from the original:
m[- ... , ]
-s
On Tue, Dec 30, 2008 at 9:59 AM, Guillaume Chapron
<carnivorescie...@gmail.com> wrote:
> m <- matrix(1:20, nrow = 10, ncol = 2)
> [,1] [,2]
> [1,] 1 11
> [2,] 2 12
> [3,] 3 13
> [4,] 4 14
> [5,] 5 15
> [6,] 6 16
> [7,] 7 17
> [8,] 8 18
> [9,] 9 19
> [10,] 10 20
>
> Then, I want to remove randomly 2 rows among the ones where m[,1]<8 and
> m[,2]>12
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