Hi Denes, It works perfectly as I want!
Thanks a lot. On Fri, Oct 12, 2018 at 6:29 AM Dénes Tóth <toth.de...@kogentum.hu> wrote: > > > On 10/12/2018 12:12 AM, roslinazairimah zakaria wrote: > > Dear r-users, > > > > I have this data: > > > > structure(list(STUDENT_ID = structure(c(1L, 1L, 1L, 1L, 1L, 1L, > > 2L, 2L, 2L, 2L, 2L), .Label = c("AA15285", "AA15286"), class = "factor"), > > COURSE_CODE = structure(c(1L, 2L, 5L, 6L, 7L, 8L, 2L, 3L, > > 4L, 5L, 6L), .Label = c("BAA1113", "BAA1322", "BAA2113", > > "BAA2513", "BAA2713", "BAA2921", "BAA4273", "BAA4513"), class = > > "factor"), > > PO1M = c(155.7, 48.9, 83.2, NA, NA, NA, 48.05, 68.4, 41.65, > > 82.35, NA), PO1T = c(180, 70, 100, NA, NA, NA, 70, 100, 60, > > 100, NA), PO2M = c(NA, NA, NA, 37, NA, NA, NA, NA, NA, NA, > > 41), PO2T = c(NA, NA, NA, 50, NA, NA, NA, NA, NA, NA, 50), > > X = c(NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA), X.1 = c(NA, > > NA, NA, NA, NA, NA, NA, NA, NA, NA, NA)), .Names = c("STUDENT_ID", > > "COURSE_CODE", "PO1M", "PO1T", "PO2M", "PO2T", "X", "X.1"), class = > > "data.frame", row.names = c(NA, > > -11L)) > > > > I want to combine the same Student ID and add up all the values for PO1M, > > PO1T,...,PO2T obtained by the same ID. > > dat <- structure(list(STUDENT_ID = structure(c(1L, 1L, 1L, 1L, 1L, 1L, > 2L, 2L, 2L, 2L, 2L), .Label = c("AA15285", "AA15286"), class = "factor"), > COURSE_CODE = structure(c(1L, 2L, 5L, 6L, 7L, 8L, 2L, 3L, > 4L, 5L, 6L), .Label = c("BAA1113", "BAA1322", "BAA2113", > "BAA2513", "BAA2713", "BAA2921", "BAA4273", "BAA4513"), class = > "factor"), > PO1M = c(155.7, 48.9, 83.2, NA, NA, NA, 48.05, 68.4, 41.65, > 82.35, NA), PO1T = c(180, 70, 100, NA, NA, NA, 70, 100, 60, > 100, NA), PO2M = c(NA, NA, NA, 37, NA, NA, NA, NA, NA, NA, > 41), PO2T = c(NA, NA, NA, 50, NA, NA, NA, NA, NA, NA, 50), > X = c(NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA), X.1 = c(NA, > NA, NA, NA, NA, NA, NA, NA, NA, NA, NA)), .Names = c("STUDENT_ID", > "COURSE_CODE", "PO1M", "PO1T", "PO2M", "PO2T", "X", "X.1"), class = > "data.frame", row.names = c(NA, > -11L)) > > # I assume you would like to add up the values with na.rm = TRUE > meanFn <- function(x) mean(x, na.rm = TRUE) > > # see ?aggregate > aggregate(dat[, c("PO1M", "PO1T", "PO2M")], > by = dat["STUDENT_ID"], > FUN = meanFn) > > # if you have largish or large data > library(data.table) > dat2 <- as.data.table(dat) > dat2[, lapply(.SD, meanFn), > by = STUDENT_ID, > .SDcols = c("PO1M", "PO1T", "PO2M")] > > > Regards, > Denes > > > > > > How do I do that? > > Thank you for any help given. > > > -- *Roslinazairimah Zakaria* *Tel: +609-5492370; Fax. No.+609-5492766* *Email: roslinazairi...@ump.edu.my <roslinazairi...@ump.edu.my>; roslina...@gmail.com <roslina...@gmail.com>* Faculty of Industrial Sciences & Technology University Malaysia Pahang Lebuhraya Tun Razak, 26300 Gambang, Pahang, Malaysia [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.