>Subject: Extracting Specific Rows of a matrix
>
>I want to create a matrix with the rows of x that have a zero in the first
>column.
>
> I tried ' if()' but this only used the first element of x.
>
>'Ifelse' does identify the rows that meet the condition but needs some value
>for the else part.
>
>Any suggestions of vectorized ways of doing this?
>
>Thanks
>
>Kirthi Kalyanam
If m is your matrix:
x <- seq(m[,1])[m[,1] == 0]
gives you a vector of all the rows for which the condition is true, and
m[x,]
will thus give you a matrix containing all the rows where the first column is
exactly zero.
Lyle Lofgren
Rosemount Inc.
Chanhassen MN