Thank you for the suggestion, Bill. The result is not quite what I would like. Here's sample code for you or anyone else who may be interested:
Al1 = c('A','C','C','C') Al2 = c('G','G','G','T') Freq1 = c(0.0078,0.0567,0.9434,0.9908) MAF = c(0.0078,0.0567,0.0566,0.0092) m1 = data.frame(Al1=Al1, Al2=Al2,Freq1=Freq1,MAF=MAF,major_allele='') m1 Al1 Al2 Freq1 MAF major_allele 1 A G 0.0078 0.0078 2 C G 0.0567 0.0567 3 C G 0.9434 0.0566 4 C T 0.9908 0.0092 Using the suggestion involving "with()" (I swapped Al1 and Al2 from before, but this does not affect the nature of the output): m1$major_allele <- with(m1, ifelse(Freq1==MAF, Al2, Al1));m1 Al1 Al2 Freq1 MAF major_allele 1 A G 0.0078 0.0078 1 2 C G 0.0567 0.0567 1 3 C G 0.9434 0.0566 2 4 C T 0.9908 0.0092 2 The output I desire is: Al1 Al2 Freq1 MAF major_allele 1 A G 0.0078 0.0078 G 2 C G 0.0567 0.0567 G 3 C G 0.9434 0.0566 C 4 C T 0.9908 0.0092 C Jim -----Original Message----- From: William Dunlap [mailto:wdun...@tibco.com] Sent: Monday, November 29, 2010 10:02 AM To: Jim Moon Subject: RE: [R] how to use by() ? m1$major_allele <- with(m1, ifelse(Freq1==MAF, Al1, Al2)) Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of Jim Moon > Sent: Monday, November 29, 2010 9:44 AM > To: r-help@r-project.org > Subject: [R] how to use by() ? > > Hello, All! > > How might one accomplish this using the by() function? > m1 is a data frame. > > # populate column "m1$major_allele" > for ( i in 1:length(m1$major_allele)) { > if ( m1$Freq1[i] == m1$MAF[i]){ > m1$major_allele[i] = m1$Al1[i] > } > else{ > m1$major_allele[i] = m1$Al2[i] > } > } > > > Jim > > [[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.