On Jun 20, 2011, at 3:54 PM, Costis Ghionnis wrote:

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

Try:

> m[y==1,1:4]<-rep( c(1,2,3,4), each= sum(y==1) )
> m
     [,1] [,2] [,3] [,4]
[1,]    1    2    3    4
[2,]    1    2    3    4
[3,]    1    2    3    4
[4,]    0    0    0    0
[5,]    0    0    0    0

-- David.

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...

______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT

______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Reply via email to