I would have used
1) != rather than ! ... ==
2) !(names(my.df) %in% "DrHorrible") since that handles NA names
(possible, but not easy to get) better.
and note that
3) subset(my.df, select = -DrHorrible) works.
On Mon, 23 Feb 2009, Petr PIKAL wrote:
Hi
r-help-boun...@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.bre...@googlemail.com
To: r-help@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
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--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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