R help - Apr 2011 - Expanding a VCV Matrix

Dear all, I have special task to expand a given VCV matrix, however
could not accomplice yet. Let say I have following VCV matrix
> mat  <- matrix(c(1,2,0,2,5,0.5,0,0.5,3), 3, 3)
> colnames(mat) <- rownames(mat) <- paste("variable", 1:3)
> mat
           variable 1 variable 2 variable 3
variable 1          1        2.0        0.0
variable 2          2        5.0        0.5
variable 3          0        0.5        3.0

Now, say I have a general string vector like this:
> Str <- c(paste("variable", 1:4), "variable2")
> Str
[1] "variable 1" "variable 2" "variable 3"
"variable 4" "variable 2"

Now according to this string, I want my previous VCV matrix also
expands. Therefore, as "variable 4" is not there in VCV matrix, so it
will be ignored. Therefore final VCV matrix will be of order 4, and
will look like:

	variable 1	variable 2	variable 3	variable 2
variable 1	1	2	0	2
variable 2	2	5	0.5	5
variable 3	0	0.5	3	0.5
variable 2	2	5	0.5	5

However, I do not think it is just some straightforward expansion,
which could be done just by the subsetting mechanism of R. Is there
any idea on how can I do it for general case?

Thanks for your time,

On 20.04.2011 19:26, Maithula Chandrashekhar wrote:
> Dear all, I have special task to expand a given VCV matrix, however
> could not accomplice yet. Let say I have following VCV matrix
>
>> mat<- matrix(c(1,2,0,2,5,0.5,0,0.5,3), 3, 3)
>> colnames(mat)<- rownames(mat)<- paste("variable", 1:3)
>> mat
>             variable 1 variable 2 variable 3
> variable 1          1        2.0        0.0
> variable 2          2        5.0        0.5
> variable 3          0        0.5        3.0
>
> Now, say I have a general string vector like this:
>
>> Str<- c(paste("variable", 1:4), "variable2")
>> Str
> [1] "variable 1" "variable 2" "variable 3"
"variable 4" "variable 2"


If Str is like the printed one above rather than the code example, you 
can do:

  mat[Str[Str %in% rownames(mat)], Str[Str %in% colnames(mat)]]

Uwe Ligges



> Now according to this string, I want my previous VCV matrix also
> expands. Therefore, as "variable 4" is not there in VCV matrix,
so it
> will be ignored. Therefore final VCV matrix will be of order 4, and
> will look like:
>
> 	variable 1	variable 2	variable 3	variable 2
> variable 1	1	2	0	2
> variable 2	2	5	0.5	5
> variable 3	0	0.5	3	0.5
> variable 2	2	5	0.5	5
>
> However, I do not think it is just some straightforward expansion,
> which could be done just by the subsetting mechanism of R. Is there
> any idea on how can I do it for general case?
>
> Thanks for your time,
>
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