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$X)
does column exist?
5 messages · Omar Lakkis, Chuck Cleland, apjaworski@mmm.com +2 more
How about is.null(df$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$X)
______________________________________________ R-help at stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Chuck Cleland, Ph.D. NDRI, Inc. 71 West 23rd Street, 8th floor New York, NY 10010 tel: (212) 845-4495 (Tu, Th) tel: (732) 452-1424 (M, W, F) fax: (917) 438-0894
There may be a simpler way, but this
is.na(match("X", names(df)))
should return TRUE if the column name exists and FALSE otherwise.
Cheers,
Andy
__________________________________
Andy Jaworski
518-1-01
Process Laboratory
3M Corporate Research Laboratory
-----
E-mail: apjaworski at mmm.com
Tel: (651) 733-6092
Fax: (651) 736-3122
Omar Lakkis
<uofiowa at gmail.co
m> To
Sent by: r-help at stat.math.ethz.ch
r-help-bounces at st cc
at.math.ethz.ch
Subject
[R] does column exist?
05/19/2005 12:42
PM
Please respond to
Omar Lakkis
<uofiowa at gmail.co
m>
How do I test if a data.frame has a column named X?
exists(o) checks if the object exists or not, I want to test if a
data.frame object (df) has a column names(X), something like:
exists(df$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
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