search for: era1end

...f another of the columns in the data frame. The only way I could figure out to do this was to subset the data frame five times, do the variable construction, and then rbind the subsets back together. Here's part of the code I used: read001 <- read[read$existstr=="001",] read001$era1end <- NA read001$era2base <- NA read001$era2end <- NA read001$era3base <- read001$era1base read001$era3end <- read001$era3base + (6 * read001$era3tr) read011 <- read[read$existstr=="011",] read011$era1end <- NA read011$era2base <- read011$era1base read...