Message-ID: <20090205214909.GA9633@localhost>
Date: 2009-02-05T21:49:09Z
From: Philipp Pagel
Subject: subset problem (reducing from six to two levels)
In-Reply-To: <21861044.post@talk.nabble.com>
On Thu, Feb 05, 2009 at 01:01:59PM -0800, Ine wrote:
>
> Hi all,
> I have got a seemingly simple problem (I am an R starter) with subsetting my
> data set, but cannot figure out the solution: I want to subset a data set
> from six to two levels, so that all analyses are done only with these two
> remaining levels.
> I tried
>
> TOTAL<-read.delim('total.csv',header=T)
> SUBSET.OF.TOTAL<-subset(TOTAL, FactorX %in% c("Level1","Level2"))
> attach(SUBSET.OF.TOTAL)
>
> but R does not eliminate the remaining levels of FactorX,
One solution is to have the factors re-built after subsetting:
foo = factor(c('a','a','b','c','c'))
# unused levels persistent:
> foo[foo=='a']
[1] a a
Levels: a b c
# but:
> factor(foo[foo=='a'])
[1] a a
Levels: a
cu
Philipp
--
Dr. Philipp Pagel
Lehrstuhl f?r Genomorientierte Bioinformatik
Technische Universit?t M?nchen
Wissenschaftszentrum Weihenstephan
85350 Freising, Germany
http://mips.gsf.de/staff/pagel