[R] extracting rows of a dataframe
Patrick Burns
pburns at pburns.seanet.com
Fri Dec 2 12:11:12 CET 2005
The key things here are:
1) a data frame is a list with some attributes (unlike a
matrix which is (generally) an atomic vector with attributes).
2) 'as.vector' removes attributes.
Patrick Burns
patrick at burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of S Poetry and "A Guide for the Unwilling S User")
Robin Hankin wrote:
>Hi
>
>look at the following session, in which I have a dataframe,
>and I want to extract the second row, without the first column.
>
>Everything works as expected until the last line, where I set
>the names of x to NULL, and get a non-desired object (I
>want c(4,3).).
>
>
>Three questions:
>
>(1) why is as.vector(a[2,-1]) not a vector?
>
>(2) How come setting names to NULL gives me bad weirdness?
>
>(3) Can I structure my dataframe in a better way, so that
>this problem does not occur?
>
>
>
>
> > a <- data.frame(male=c(T,T,F),mass=c(1,4,3),height=c(4,3,2))
> > a
> male mass height
>1 TRUE 1 4
>2 TRUE 4 3
>3 FALSE 3 2
> > x <- as.vector(a[2,-1])
> > x
> mass height
>2 4 3
> > names(x) <- NULL
> > x
> structure("4", class = "AsIs") structure("3", class = "AsIs")
>2 4 3
> >
>
>--
>Robin Hankin
>Uncertainty Analyst
>National Oceanography Centre, Southampton
>European Way, Southampton SO14 3ZH, UK
> tel 023-8059-7743
>
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