Expanding a VCV Matrix

Thanks Uwe for your insight. However this could not solve my problem.
Actually, I meant to define 'Str' in this way:

mat<- matrix(c(1,2,0,2,5,0.5,0,0.5,3), 3, 3)
colnames(mat)<- rownames(mat)<- paste("variable", 1:3, sep="")
mat

           variable1 variable2 variable3
variable1         1       2.0       0.0
variable2         2       5.0       0.5
variable3         0       0.5       3.0

Str<- c(paste("variable", 1:4, sep=""), "variable2"); Str

[1] "variable1" "variable2" "variable3" "variable4" "variable2"

Therefore 'variable2' should appear twice in my modified VCV matrix,
which was not there in your suggestion. Is there any better any on how
can I do that? or it is really imposable to achieve?

Thanks,

2011/4/21 Uwe Ligges<ligges at statistik.tu-dortmund.de>:

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,