Try this: z1 <- c(1,-1,0,99)[Data$A] z2 <- c(-1,1,0,99)[Data$A] Data$new <- ifelse(Data$B == 1, z1,z2)
(This does not generalize, however, and assumes that the values you gave are exact. Gabor's approach would work more generally) -- Bert Gunter Genentech Nonclinical Statistics -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Gabor Grothendieck Sent: Tuesday, January 22, 2008 11:09 AM To: Dimitri Liakhovitski Cc: R-Help List Subject: Re: [R] recoding one variable into another - but differently fordifferent cases You could create a lookup table or use recode in the car package. Another possibility is to use a logical/arithmetic expression. The following expression says that - if A is 1 then use the first term equals the coefficient, namely 1 if B ==1 and -1 if B == 2. Also, if A is not 1 then that term is zero and can be ignored. - if A is 2 or 99 then the second or third terms are used analogously - otherwise no terms are selected and the expression equals zero transform(Data, new = (A == 1) * ((B == 1) - (B == 2)) + (A == 2) * ((B == 2) - (B == 1)) + (A == 4) * 99) This could be reduced even more although at the expense of understandability, e.g. transform(Data, new = ifelse(A > 2, 99 * (A == 4), (A == B) - (A != B))) On Jan 22, 2008 12:25 PM, Dimitri Liakhovitski <[EMAIL PROTECTED]> wrote: > Hello, > I have 2 variables in my sample Data: Data$A and Data$B > Variable Data$A can assume values: 1, 2, 3, and 4. > Variable Data$B identifies my cases and can assume values: 1 and 2. > > I need to recode my variable Data$A into a new variable Data$new such that: > > People who are Data[Data$B %in% 1, ] are recoded like this: > > Value on Data$A Value on Data$new > 1 +1 > 2 -1 > 3 0 > 4 99 > > People who are Data[Data$B %in% 2, ] are recoded like this: > > Value on Data$A Value on Data$new > 1 -1 > 2 +1 > 3 0 > 4 99 > > I am having hard time doing this. Any help would be greatly appreciated. > Dimitri > > ______________________________________________ > [email protected] 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. > ______________________________________________ [email protected] 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. ______________________________________________ [email protected] 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.
