How do I test if a data.frame has a column named X? exists(o) checks if the object exists or not, I want to test if a data.frame object (df) has a column names(X), something like: exists(df$X)
How about is.null(df$X)==FALSE ? Omar Lakkis wrote:> How do I test if a data.frame has a column named X? > exists(o) checks if the object exists or not, I want to test if a > data.frame object (df) has a column names(X), something like: > exists(df$X) > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > >-- Chuck Cleland, Ph.D. NDRI, Inc. 71 West 23rd Street, 8th floor New York, NY 10010 tel: (212) 845-4495 (Tu, Th) tel: (732) 452-1424 (M, W, F) fax: (917) 438-0894
There may be a simpler way, but this
is.na(match("X", names(df)))
should return TRUE if the column name exists and FALSE otherwise.
Cheers,
Andy
__________________________________
Andy Jaworski
518-1-01
Process Laboratory
3M Corporate Research Laboratory
-----
E-mail: apjaworski at mmm.com
Tel: (651) 733-6092
Fax: (651) 736-3122
Omar Lakkis
<uofiowa at gmail.co
m> To
Sent by: r-help at stat.math.ethz.ch
r-help-bounces at st cc
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Subject
[R] does column exist?
05/19/2005 12:42
PM
Please respond to
Omar Lakkis
<uofiowa at gmail.co
m>
How do I test if a data.frame has a column named X?
exists(o) checks if the object exists or not, I want to test if a
data.frame object (df) has a column names(X), something like:
exists(df$X)
______________________________________________
R-help at stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
It depends on what Omar means by "a column named X". Consider the
following:
> tstDF <- data.frame(aa=1, bb=2)
> tstDF$a
[1] 1
> is.null(tstDF$a)
[1] FALSE
> is.na(match("a", names(tstDF)))
[1] TRUE
Does tstDF have a column named "a"? It has a column named
"aa",
which is accessed by tstDF$a; is.null(tstDF$a) correctly identifies its
presence, while is.na(match("a", names(tstDF))) correctly says that
"a"
is not the official name of any column of tstDF.
spencer graves
apjaworski at mmm.com wrote:
>
>
>
>
> There may be a simpler way, but this
>
> is.na(match("X", names(df)))
>
> should return TRUE if the column name exists and FALSE otherwise.
>
> Cheers,
>
> Andy
>
> __________________________________
> Andy Jaworski
> 518-1-01
> Process Laboratory
> 3M Corporate Research Laboratory
> -----
> E-mail: apjaworski at mmm.com
> Tel: (651) 733-6092
> Fax: (651) 736-3122
>
>
>
> Omar Lakkis
> <uofiowa at gmail.co
> m>
To
> Sent by: r-help at stat.math.ethz.ch
> r-help-bounces at st
cc
> at.math.ethz.ch
> Subject
> [R] does column exist?
> 05/19/2005 12:42
> PM
>
>
> Please respond to
> Omar Lakkis
> <uofiowa at gmail.co
> m>
>
>
>
>
>
>
> How do I test if a data.frame has a column named X?
> exists(o) checks if the object exists or not, I want to test if a
> data.frame object (df) has a column names(X), something like:
> exists(df$X)
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
On Thu, 19 May 2005 apjaworski at mmm.com wrote:> There may be a simpler way, but this > > is.na(match("X", names(df))) > > should return TRUE if the column name exists and FALSE otherwise.Mere syntactic sugar, but "X" %in% names(mydf) is self-documenting.> How do I test if a data.frame has a column named X? > exists(o) checks if the object exists or not, I want to test if a > data.frame object (df) has a column names(X), something like: > exists(df$X)-- 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