[R] selective subsetting of a correlation matrix

[Romain Francois]

On 12/04/2009 02:24 PM, Romain Francois wrote:
>
> On 12/04/2009 02:18 PM, Lee William wrote:
>>
>> Dear All,
>> I have a correlation matrix say 'M' (4000x4000) for 4000 genes and I
>> want to
>> subset it to 'N' (190x190) for 190 genes.
>> The list of those 190 genes are in variable 't'. So the idea is to
>> read the
>> names of genes from variable 't' and subset the matrix M accordingly.
>> Any thoughts are welcome!
>>
>> Best
>> Lee
>
> Hi,
>
> Assuming the correlation matrix has dimnames, you can do :
>
> x[ rownames(x) %in% t, colnames(x) %in% t ]
>
> Here is a reproducible example, please make sure you provide one next time.
>
> x <- expand.grid( x1 = 1:2, x2 = 1:2, x3 = 1:2, x4 = 1:2 )
> y <- cor( x )
> t <- c("x1", "x2")
> y[ rownames(y) %in% t, colnames(y) %in% t ]

Or even : y[t,t]

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Romain Francois
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