Hello, I searched the archives but could not come to a solution. I have to two columns of information
t_start_cdt looks like: > t_start_cdt[1:4] [1] "2003-07-09 11:02:25" "2003-07-09 11:10:25" "2003-07-09 11:30:25" [4] "2003-07-09 12:00:25" > class(t_start_cdt) [1] "POSIXt" "POSIXlt" t_end_cdt looks like: > t_end_cdt[1:4] [1] "2003-07-09 11:02:35" "2003-07-09 11:10:35" "2003-07-09 11:30:35" [4] "2003-07-09 12:00:35" > class(t_end_cdt) [1] "POSIXt" "POSIXlt" I'd like to estimate the mean of each "pair". For example, the mean of (t_start_cdt[1] and t_end_cdt[1]). The only way I could do this is: hi <- cbind(as.matrix(as.POSIXct(t_start_cdt)), as.matrix(as.POSIXct(t_end_cdt))) hi <- apply(hi, MARGIN=1, FUN=mean) class(hi) <- c("POSIXt", "POSIXct") t_mean_cdt <- as.POSIXlt(hi) rm(hi) What am I missing conceptually about POSIXlt, and what is the better method? thanks, Mike ______________________________________________ [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