Re: [R] sorting & subsetting a data.frame

From: Dennis Murphy <djmuser_at_gmail.com>
Date: Sun, 06 Mar 2011 15:35:59 -0800

Hi:

One approach is through the data.table package:

library(data.table)
df <- as.data.frame(data.table(iris, key = 'Species')[Sepal.Length == 6.7]) str(df)

Using Species as a key variable automatically sorts by Species; the bracketing allows you to subset on Sepal.Length == 6.7.

ddply() in the plyr package also works:

library(plyr)
ddply(iris, .(Species), subset, Sepal.Length == 6.7)

HTH,
Dennis

On Sun, Mar 6, 2011 at 2:49 PM, Liviu Andronic <landronimirc_at_gmail.com>wrote:

> Dear all
> This may be obvious, but I cannot get it working. I'm trying to subset
> & sort a data frame in one go.
> x <- iris
> x$Species1 <- as.character(x$Species)
> ##subsetting alone works fine
> with(x, x[Sepal.Length==6.7,])
> ##sorting alone works fine
> with(x, x[order(Sepal.Length, rev(sort(Species1))),])
> ##gets subsetted, but not sorted as expected
> with(x, x[(Sepal.Length==6.7) & order(Sepal.Length, rev(sort(Species1))),])
> ##gets subsetted, but sorts very strangely
> xa <- with(x, x[Sepal.Length==6.7,]); with(xa, xa[order(Sepal.Length,
> rev(sort(Species1))),])
> xa <- with(x, x[Sepal.Length==6.7,]); with(xa,
> xa[order(rev(sort(Species1))),])
>
> I've checked The R Inferno, Quick-R and several other places with no
> obvious solution.
>
> Any ideas? Regards
> Liviu
>
>
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