I usually do this kind of thing like this: variable3 <- rep(1,length(variable1.fac)) variable3[ variable1.fac == 0 & variable2.num >= 1 ] <- 2 variable3[ variable1.fac == 1 & variable2.num == 0 ] <- 3 variable3[ variable1.fac == 1 & variable2.num >= 1 ] <- 4
This approach is easy to read and understand, and I would (personally) consider it analogous to the SPSS approach. This approach does require that the variables all have the same length -- which may be intrinsically built in to the SPSS data structure, but is not guaranteed in R (unless all of the variables are contained in a data frame). The key concept is that in R, the if() function is for logical objects of length=1, only. The ifelse() function is for logical objects of length > 1. In R terminology, we would say that ifelse() is a vectorized function, but if() is not. The SPSS if function appears to behave in a vectorized manner. Although nested ifelse() functions can be used in this case, I find them harder to read. -Don -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062 On 1/2/12 1:11 AM, "Richard Kolodziej" <richard.kolodz...@web.de> wrote: >Hello, > >I'm using SPSS at work but really would like to switch to R. Right now I'm >trying to learn R in reproducing calculations I did with SPSS but am stuck >with something that is quite simple and comprehensible in SPSS-Syntax: > >IF (variable1.fac = 0 AND variable2.num = 0) variable3=1. >IF (variable1.fac = 0 AND variable2.num >= 1) variable3=2. >IF (variable1.fac = 1 AND variable2.num = 0) variable3=3. >IF (variable1.fac = 1 AND variable2.num >= 1) variable3=4. > >I want to create four different groups out of different conditions of two >variables: > * variable1.fac is a factor coded with 0 and 1 > * variable2.num is a numerical variable with only whole numbers > >My problem with R is that I can't find a way to use AND in an IF statement >that doesn't produce an error or not intended solutions. > >"An Introduction to R" is really unhelpful with this problem and I >wouldn't >have written here, if I didn't have searched for the answer. > >http://tolstoy.newcastle.edu.au/R/help/05/09/12136.html was helpful in >understanding how the IF statement is written in R but didn't answer my >question how to add an usable AND (&, |) >https://stat.ethz.ch/pipermail/r-help/2008-November/178808.html looked >promising but didn't do what I had intended > >Thanks in advance, >Richard > > [[alternative HTML version deleted]] > >______________________________________________ >R-help@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@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.
