[R] manipulating a matrix

[David Winsemius]

On May 12, 2010, at 3:14 PM, Clark Johnston wrote:

>
> Is there a way to create a new matrix from and existing matrix with
>
> A
>          [,1]     [,2]
> [1,]      1        13
> [2.]      2        18
> [3,]      3        14
> [4,]      4        20
>
> if()
>
> B
>       [,1]   [,2]
> [1,]   2      18
> [2,]   4      20

Try (untested absent reproducible example);

A[A[,2] > 15, ]

This (should) create a logical vector in the first argument to "["  
which has the effect of returning the rows for which that vector is  
TRUE.

>
>
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David Winsemius, MD
West Hartford, CT