[R] Filtering a data frame using a string for colum header

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 23.02.2009 03:44:41:

> 
> Hi Tony,
> 
> I "GUESS" my.df[-"DrHorrible"] does not tell R which column "NUMBER" 
would 
> like to remove.
> As we know, we could use my.df[-4] and it exactly tells R which column 
must 
> remvoer from your data.
> 
>  > my.df[-4]
>   Angel Buffy Firefly
> 1     7     8       9
> 2     8     9       9
> 3     6     4      10
> 4     9     9      10
> 5    10    10      10
> 
> 
> I may be not right. 

It is a bit deeper than [] selection.

> -"DrHorrible"
Error in -"DrHorrible" : invalid argument to unary operator, so the error 
is within selection operator [...].

If you know the name and you do not want column with this particular name 
use

my.df[,!names(my.df)==("DrHorrible")]

Regards
Petr


> 
> 
> 
> Chunhao
> 
> 
> 
> 
> 
> 
> 
> 
> > Date: Sun, 22 Feb 2009 14:48:10 -0800
> > From: tony.breyal at googlemail.com
> > To: r-help at r-project.org
> > Subject: [R] Filtering a data frame using a string for colum header
> > 
> > Hi all,
> > 
> > I was just radomly playing with R and got the following error when
> > trying to filter a data frame using a string:
> > 
> > > Angel <- c(7,8,6,9,10)
> > > Buffy <- c(8,9,4,9,10)
> > > Firefly <- c(9,9,10,10,10)
> > > DrHorrible <- c(10,9,9,10,10)
> > > my.df <- data.frame(Angel, Buffy, Firefly, DrHorrible)
> > > my.df["DrHorrible"]
> > DrHorrible
> > 1 10
> > 2 9
> > 3 9
> > 4 10
> > 5 10
> > > my.df[-"DrHorrible"]
> > Error in -"DrHorrible" : invalid argument to unary operator
> > >
> > 
> > I know how to work around this problem quite easily, I'm just curious
> > as to why the my.df[-"DrHorrible] statement didn't work?
> > 
> > Cheers,
> > Tony
> > 
> > OS = win XP
> > > sessionInfo()
> > R version 2.8.1 (2008-12-22)
> > i386-pc-mingw32
> > 
> > locale:
> > LC_COLLATE=English_United Kingdom.1252;LC_CTYPE=English_United 
Kingdom.
> > 1252;LC_MONETARY=English_United Kingdom.
> > 1252;LC_NUMERIC=C;LC_TIME=English_United Kingdom.1252
> > 
> > attached base packages:
> > [1] stats graphics grDevices utils datasets methods
> > base
> > >
> > 
> > ______________________________________________
> > 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.
> 
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