[R] does column exist?
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$X) __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] does column exist?
How about is.null(df$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$X) __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html -- Chuck Cleland, Ph.D. NDRI, Inc. 71 West 23rd Street, 8th floor New York, NY 10010 tel: (212) 845-4495 (Tu, Th) tel: (732) 452-1424 (M, W, F) fax: (917) 438-0894 __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] does column exist?
There may be a simpler way, but this is.na(match(X, names(df))) should return TRUE if the column name exists and FALSE otherwise. Cheers, Andy __ Andy Jaworski 518-1-01 Process Laboratory 3M Corporate Research Laboratory - E-mail: [EMAIL PROTECTED] Tel: (651) 733-6092 Fax: (651) 736-3122 Omar Lakkis [EMAIL PROTECTED] m To Sent by: r-help@stat.math.ethz.ch [EMAIL PROTECTED] cc at.math.ethz.ch Subject [R] does column exist? 05/19/2005 12:42 PM Please respond to Omar Lakkis [EMAIL PROTECTED] m How do I test if a data.frame has a column named X? exists(o) checks if the object exists or not, I want to test if a data.frame object (df) has a column names(X), something like: exists(df$X) __ R-help@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@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
Re: [R] does column exist?
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 [EMAIL PROTECTED] 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: [EMAIL PROTECTED] Tel: (651) 733-6092 Fax: (651) 736-3122 Omar Lakkis [EMAIL PROTECTED] m To Sent by: r-help@stat.math.ethz.ch [EMAIL PROTECTED] cc at.math.ethz.ch Subject [R] does column exist? 05/19/2005 12:42 PM Please respond to Omar Lakkis [EMAIL PROTECTED] 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$X) __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] does column exist?
On Thu, 19 May 2005 [EMAIL PROTECTED] wrote: There may be a simpler way, but this is.na(match(X, names(df))) should return TRUE if the column name exists and FALSE otherwise. Mere syntactic sugar, but X %in% names(mydf) is self-documenting. How do I test if a data.frame has a column named X? exists(o) checks if the object exists or not, I want to test if a data.frame object (df) has a column names(X), something like: exists(df$X) -- Brian D. Ripley, [EMAIL PROTECTED] 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, UKFax: +44 1865 272595 __ R-help@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
