On 16-May-10 06:11:52, Agustín Muñoz "M. (AMFOR) wrote:
> hi everybody, a question, as I can know the location (number) of an
> attribute with its name.
>
> Ej.
>
> X1 X2 X3 X4 X5 X6
> 1 3 5 2 1 7
> 6 7 4 5 2 9
>
> as I can know that the attribute "X4" is in position 4
>
> I hope you can help me
>
> from already thank you very much to all
> AgustÃn
You can use the function colnames(), with either a matrix or a
dataframe, to extract (or set) the column names:
X <- matrix(c( 1,3,5,2,1,7,6,7,4,5,2,9), byrow=TRUE,nrow=2)
colnames(X) <- c("X1","X2","X3","X4","X5","X6")
X
# X1 X2 X3 X4 X5 X6
# [1,] 1 3 5 2 1 7
# [2,] 6 7 4 5 2 9
colnames(X)
# [1] "X1" "X2" "X3" "X4" "X5" "X6"
which(colnames(X)=="X4")
# [1] 4
X <- data.frame(X1=c(1,6),X2=c(3,7),X3=c(5,4),
X4=c(2,5),X5=c(1,2),X6=c(7,9))
X
# X1 X2 X3 X4 X5 X6
# 1 1 3 5 2 1 7
# 2 6 7 4 5 2 9
colnames(X)
# [1] "X1" "X2" "X3" "X4" "X5" "X6"
which(colnames(X)=="X4")
# [1] 4
So, in either case,
which(colnames(X)=="X4")
will give the result you want.
Hoping this helps,
Ted.
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E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk>
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Date: 16-May-10 Time: 09:42:28
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