The suggestion below was made. df1$Date <- as.Date(df1$Date) df2$Date <- as.Date(df2$Date) ifelse(df1$ID==df2$ID & df1$Date-df2$Date<0.5,df1$y-df2$y, NA)
However, because my dataframe rows do not align, I need the conditionals to be tested on every combination of cells. I'm starting to think I need to use tapply? Tim -- View this message in context: http://www.nabble.com/Conditional-operation-on-multiple-columns-from-two-data-frames-tp21189891p21197566.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
