Hi
as.matrix is rather dangerous, it converts all values to lowest mode which, if
there is text column, is character.
And if I understand correctly original post was about removing all zero columns.
Using plain zero comparison can be dangerous due to possibility of compensating
negative and positive values.
> dat<-data.frame(a=c(-1,0,1), b=c(0,0,0), c=c(0,0,1))
> dat
a b c
1 -1 0 0
2 0 0 0
3 1 0 1
> colSums(dat)==0
a b c
TRUE TRUE FALSE
Remove incorrectly first column too.
I would proceed with NA substitution, which is safer.
> dat[dat==0]<-NA
> colSums(is.na(dat))==nrow(dat)
a b c
FALSE TRUE FALSE
>
And even this can be problematic if values in dat are not integers.
Cheers
Petr
> -----Original Message-----
> From: R-help [mailto:[email protected]] On Behalf Of Ulrik
> Stervbo
> Sent: Friday, January 08, 2016 6:06 PM
> To: Hiroyuki Sato; [email protected]
> Subject: Re: [R] [Q] It it possible to create the data frame only non-
> zero data column?
>
> Could you use rowsum and select rows larger then 0?
>
> Something like:
>
> result[rowsum(as.matrix(result) > 0, ]
>
> On Fri, 8 Jan 2016 at 18:00 Hiroyuki Sato <[email protected]> wrote:
>
> > Hello all.
> >
> > I re-post this question by e-mail.
> > (I posted via google-group. But It's not posted yet.)
> >
> > I'm newbie GNU R.
> >
> > I would like to compare two datas.
> > How to select columns which has non-zero datas?.
> > It it possible to create the data frame only VAL3(non-zero data)
> > column with command?
> >
> > Formatted sample.
> > https://gist.github.com/hiroyuki-sato/cb36584f6cd5845b6c3e
> >
> > sample1.txt
> >
> > ID,VAL1,VAL2,VAL3
> > ID1,0,2,3
> > ID2,0,2,3
> > ID3,0,2,3
> >
> > real data has 5000 columns.
> >
> > sample2.txt
> >
> > ID,VAL1,VAL2,VAL3
> > ID1,0,2,3
> > ID2,0,2,3
> > ID3,0,2,2
> >
> > The difference sample1 and sample2 is ID3/VAL3.
> > sample1: 3
> > sample2: 2
> >
> > R commands.
> >
> > sample1 <- read.table("sample1.txt",header=T,sep=',')
> > sample2 <- read.table("sample2.txt",header=T,sep=',')
> >
> > result <- sample1[,2:4] - sample2[,2:4]
> > result
> > VAL1 VAL2 VAL3
> > 1 0 0 0
> > 2 0 0 0
> > 3 0 0 1
> >
> > I would like to create data frame which has non-zero value columns.
> > Could you tell me how to do it?
> >
> > Best regards.
> >
> > --
> > Hiroyuki Sato.
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > [email protected] mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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