Data reshaping

Hello again, let say I have following data-frame:

Dat <- data.frame(c(rep(c("A", "B"), each = 4), "C", "C", "C"),

c(rep(1:4, 2), 1, 2, 3), 11:21)

colnames(Dat) <- c("X1", "X2", "X3")
Dat

   X1 X2 X3
1   A  1 11
2   A  2 12
3   A  3 13
4   A  4 14
5   B  1 15
6   B  2 16
7   B  3 17
8   B  4 18
9   C  1 19
10  C  2 20
11  C  3 21


Now I want to put that data-frame in the following form:

Dat1 <- rbind(c(11,12,13,14), c(15,16,17,18), c(19,20,21, NA));

colnames(Dat1) <- c(1,2,3,4); rownames(Dat1) <- c("A", "B", "C")

Dat1

   1  2  3  4
A 11 12 13 14
B 15 16 17 18
C 19 20 21 NA


Basically, 'Dat' is the melted form of 'Dat1'

Can somebody point me any R function for doing that?

Thanks for your help.

        [[alternative HTML version deleted]]