Filtering a data frame using a string for colum header
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-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
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