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. 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.