Re: [R] Matrix manipulation

From: Dennis Murphy <djmuser_at_gmail.com>
Date: Fri, 01 Apr 2011 22:56:36 -0700

Hi:

Here' s one approach:

> int <- sample(1:20,10)
> m <- matrix(sample(1:40, 20), nrow = 10)
> int

[1] 7 12 4 6 1 19 17 20 15 5
> m

[,1] [,2]

``` [1,]    9   15
[2,]   23   32
[3,]   40   14
[4,]   19   38
[5,]   28    6
[6,]   26   18
[7,]   34   22
[8,]    7   35
[9,]   21    3
```

[10,] 39 12
> m[m[, 1] %in% int, ]

[,1] [,2]
[1,] 19 38
[2,] 7 35

HTH,
Dennis

On Fri, Apr 1, 2011 at 10:08 PM, Joseph N. Paulson <josephpaulson_at_gmail.com>wrote:

> Hi all!
>
> I have a vector, let's say for example int <- sample(1:20,10);
> for now:
>
> now I have a matrix...
> M = m x n
> where the first column is a "feature" column and most likely shares at
> least
> one of the int (interesting) numbers.
>
> I want to extract the rows where int[] = M[,1]
>
> I thought:
> rownames(int)<-int;
> rownames(M)<-M[,1];
>
> M[rownames(int),] would work, but it doesn't... (I assume because I have
> rownames(M)==rownames(int)...
>
> Any help would be greatly appreciated!
>
> Thank you!
>
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>
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