?format.POSIXct Particularly %w
> x <- Sys.time() > as.numeric(format(x, "%w")) [1] 1 -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of John McKown Sent: Monday, July 7, 2014 10:54 AM To: r-help Subject: [R] getting numeric [0..6] day of week from POSIXct? I have a column, dt, in a data.frame. It is a list of POSIXct objects. I could use strftime(frame$dt,"%a") to get the day of week as [sun..sat]. But I need the numeric value in the range of [0..6]. I can't see a function to do this. I can get it by converting the POSIXct objects to POSIXlt objects, then extracting the $wday. I don't know why, but that just doesn't "feel" right to me. What I am actually trying to do is group my data by Gregorian week (Sunday..Saturday). To group the data, I am getting the ISO 8601 year and week number using strftime(dt) with the format of "%G-%V" . But the ISO year&week number start on Monday, not Sunday. So what I do is: dt <- as.POSIXlt(frame$dt); dt <- dt - dt$wday*86400; # 86400 is seconds in a day frame$groupByWeekNumber <- strftime(dt,"%G-%V"); is there a better way? I have tried my best to find a simpler way. -- There is nothing more pleasant than traveling and meeting new people! Genghis Khan Maranatha! <>< John McKown ______________________________________________ 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.
