Hi:

Here's an example:

m <- as.data.frame(matrix(rnorm(10000), nrow = 100))
dim(m)
[1] 100 100
# Assign rownames to rows of m
rownames(m) <- paste('A', 1:100, sep = '')

# Select a random subset of the rownames
vn <- sample(rownames(m), 50)

# Subset m by selecting the rownames from vn
m2 <- m[rownames(m) %in% vn, ]

# Did we get the right ones?
identical(sort(vn), sort(rownames(m2)))
[1] TRUE

HTH,
Dennis

On Wed, Apr 13, 2011 at 9:13 AM, pankaj borah <pankajborah2k3@yahoo.co.in>wrote:

> I have a matrix M
>
> > dim(M)
>
> [1] 30380   561
>
> I have another list L contains , that contains some row names of matrix M
> str (L)
>  chr [1:21037]
>
> Now I want to extract the submatrix subM (21037    ,    561)  from the
> matrix M by matching the rownames (M) to the 21037 rownames o f L
>
> How do I do that ?
>
> Thanks and regards,
>
> Pankaj Barah
>
>
>
>
> Pankaj Barah Department of Biology
>  Norwegian University of Science & Technology (NTNU)
>   Realfagbygget, N-7491 Trondheim, Norway T
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>
>
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