Hi Cruz
you don't need to assign dimension or classes to your objects.
It's easier if you do like this
> a=c(0,1,2,4,1,1)
> length(a)
[1] 6
> b=matrix(a,3,2,byrow=T)
> b
[,1] [,2]
[1,] 0 1
[2,] 2 4
[3,] 1 1
of course you can change the colnames and assign what
you prefer
> colnames(b)=c("x","y")
but if you try to recall "x" with
b$x
is not going to work
like that,
you have two option:
1. switch form matrix to a dataframe:
> c=as.data.frame(b)
> c
x y
1 0 1
2 2 4
3 1 1
> c$x
[1] 0 2 1
no problems.
2. Can get the column "x"
on the matrix b as
b[,1]
[1] 0 2 1
just giving the position.
Hope that this helps.
Best Regards
Anna
Anna Freni Sterrantino
Ph.D Student
Department of Statistics
University of Bologna, Italy
via Belle Arti 41, 40124 BO.
________________________________
Da: cruz <[EMAIL PROTECTED]>
A: r-help@r-project.org
Inviato: Giovedì 6 novembre 2008, 17:22:42
Oggetto: [R] How to avoid "$ operator is invalid for atomic vectors"
Hi,
I am writing this in a wrong way, can someone please correct me?
> A <- matrix()
> length(A) <- 6
> dim(A) <- c(3,2)
> colnames(A) <- c("X","Y")
> A
X Y
[1,] NA NA
[2,] NA NA
[3,] NA NA
> A$X
Error in A$X : $ operator is invalid for atomic vectors
>
Thanks,
cruz
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