[R] adding column to data frame conditionally

ONKELINX, Thierry Thierry.ONKELINX at inbo.be
Thu May 27 11:38:32 CEST 2010

Dear Kristina,

Use ifelse(). Note that you must use '==' to test for equality. '=' is
an assignment.

Freqg$condition <- with(freqg, ifelse(mat==1 & flank==1, 1, ifelse(mat
== 2 & flank == 1, 2, NA)))



ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek
team Biometrie & Kwaliteitszorg
Gaverstraat 4
9500 Geraardsbergen

Research Institute for Nature and Forest
team Biometrics & Quality Assurance
Gaverstraat 4
9500 Geraardsbergen

tel. + 32 54/436 185
Thierry.Onkelinx op inbo.be

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> -----Oorspronkelijk bericht-----
> Van: r-help-bounces op r-project.org 
> [mailto:r-help-bounces op r-project.org] Namens Kristina Schmitz
> Verzonden: donderdag 27 mei 2010 11:33
> Aan: r-help op r-project.org
> Onderwerp: [R] adding column to data frame conditionally
> Dear all and thanks in advance for helping me with a rather 
> stupid question:
> I imported a data set ("freqg") into R consisting of 14 
> variables. Now a want to compute a variable and add it in an 
> additional column to my data frame. The value of this new 
> variable ("condition") depends on the values of two other 
> variables ("mat" and "flank") already included in the data frame.
> For example:
> if mat=1 and flank=1 -> condition=1
> if mat=2 and flank=1 -> condition=2
> ...
> What I got is this code, which doesn't really work (it 
> results in a new column called "condition" which takes only 
> the value "TRUE"):
> freqg<-transform(freqg,condition=(mat=1)&(flank=1))
> Thanks in advance and kind regards!
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> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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