[R] matrix problem

[Costis Ghionnis]

Hallo everyone! I have a problem about creating a matrix...

Suppose we have a vector y<-c(1,1,1,3,2)

and a zero matrix, m ,with nrows=length(y) and ncol=4.

The matrix would look like this:
0	0	0	0
0	0	0	0
0	0	0	0
0	0	0	0
0	0	0	0

I want to change the first three rows with the vector c(1,2,3,4).
I thought that with the command m[y==1,1:4]<-c(1,2,3,4) i would get

1	2	3	4
1	2	3	4
1	2	3	4
0	0	0	0
0	0	0	0

but instead i am getting

1	4	3	2
2	1	4	3
3	2	1	4
0	0	0	0
0	0	0	0

It seems it is filling the data by col instead by row. I want to use this technique in more complicated problems.
So i do not want to have to work with the transpose matrix. Do you know another way to make this work. Thank you...