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

An embedded and charset-unspecified text was scrubbed...
Name: not available
URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20090223/c2d1740c/attachment-0001.pl>
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.

_________________________________________________________________
[[elided Hotmail spam]]

   [[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.
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.

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.

_________________________________________________________________
[[elided Hotmail spam]]

   [[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.

______________________________________________
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.

Brian D. Ripley,                  ripley at 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
Cheers guys,

yeah, I was using this bit of code as my work around:
filter.col <- which(names(my.df)!="DrHorrible")
my.df[filter.col]
but you guys had better solutions  :-)

Is there an R wish list somewhere? I tried google but couldn't find a
specific location, just various threads here and there. It just seems
to me that if
my.df2["DrHorrible"]
works, then
my.df2[-"DrHorrible"]
should work too, in the same way that my.df2[-2] would.

Thanks again, always good to learn new and better ways of doing
things,
Tony Breyal
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... 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.bre... at googlemail.com
To: r-h... 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-h... 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.

_________________________________________________________________
[[elided Hotmail spam]]

? ?[[alternative HTML version deleted]]

______________________________________________
R-h... 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.

______________________________________________
R-h... at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guidehttp://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
Brian D. Ripley, ? ? ? ? ? ? ? ? ?rip... at 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

______________________________________________
R-h... at r-project.org mailing listhttps://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guidehttp://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.