[R] How to avoid "$ operator is invalid for atomic vectors"
Nordlund, Dan (DSHS/RDA)
NordlDJ at dshs.wa.gov
Thu Nov 6 19:04:49 CET 2008
> -----Original Message-----
> From: r-help-bounces at r-project.org
> [mailto:r-help-bounces at r-project.org] On Behalf Of anna freni
> sterrantino
> Sent: Thursday, November 06, 2008 10:00 AM
> To: cruz; r-help at r-project.org
> Subject: Re: [R] How to avoid "$ operator is invalid for
> atomic vectors"
>
> 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 <cruadam at gmail.com>
> A: r-help at r-project.org
> Inviato: GiovedÃ¬ 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
>
You can also use the column name with the matrix
A[,'X']
Hope this is helpful,
Dan
Daniel J. Nordlund
Washington State Department of Social and Health Services
Planning, Performance, and Accountability
Research and Data Analysis Division
Olympia, WA 98504-5204
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