[R] request: How to get column name

[Petr PIKAL]

r-help-bounces at r-project.org napsal dne 03.09.2008 17:34:24:

> On 9/3/2008 11:05 AM, Petr PIKAL wrote:
> > r-help-bounces at r-project.org napsal dne 03.09.2008 15:54:08:
> > 
> >> try this:
> >>
> >> x <- c(3,3,3,3,0,0,0,0,5,5,5,5,8,8,8,8)
> >> x <- matrix(x, nrow=4)
> >>
> >> which(colSums(x == 0) == nrow(x))
> > 
> > Isn't this the same?
> > 
> > which(colSums(x)==0)
> 
>   No, because the column sum can be zero without each element being 
zero:
> 

OK you got me.
What about

which(colSums(abs(x))==0)

and yes, I am aware of floating point arithmetic, so better approach would 
be

which(colSums(abs(x))<some.small.value)

Regards
Petr

> x <- c(3,3,3,3,1,-1,1,-1,5,5,5,5,8,8,8,8)
> x <- matrix(x, nrow=4)
> 
> > which(colSums(x == 0) == nrow(x))
> integer(0)
> 
> > which(colSums(x)==0)
> [1] 2
> 
> > Regards
> > Petr
> > 
> >> I hope it helps.
> >>
> >> Best,
> >> Dimitris
> >>
> >>
> >> Muhammad Azam wrote:
> >>> Dear R community
> >>> I have a problem regarding which of the column in a matrix contains 
> > all of 
> >> zero elements. e.g.
> >>> x=c(3,3,3,3,0,0,0,0,5,5,5,5,8,8,8,8); x=matrix(x, nrow=4)
> >>> the output is
> >>>
> >>>> x
> >>>>
> >>>      [,1] [,2] [,3] [,4]
> >>> [1,]    3    0    5    8
> >>> [2,]    3    0    5    8
> >>> [3,]    3    0    5    8
> >>> [4,]    3    0    5    8
> >>> In this case the required column is second so the result should be 
> > "2". How 
> >> can i get it? 
> >>>
> >>> best regards
> >>>
> >>> Muhammad Azam 
> >>>
> >>>
> >>>
> >>>
> >>>    [[alternative HTML version deleted]]
> >>>
> >>> ______________________________________________
> >>> R-help at r-project.org mailing list
> >>> 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.
> >>>
> >>>
> >>
> >> -- 
> >> Dimitris Rizopoulos
> >> Assistant Professor
> >> Department of Biostatistics
> >> Erasmus University Medical Center
> >>
> >> Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
> >> Tel: +31/(0)10/7043399
> >> Fax: +31/(0)10/7044657
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list
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> >> PLEASE do read the posting guide 
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> > 
> > ______________________________________________
> > R-help at r-project.org mailing list
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> > PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> > 
> 
> 
> -- 
> Chuck Cleland, Ph.D.
> NDRI, Inc. (www.ndri.org)
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> ______________________________________________
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> PLEASE do read the posting guide 
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