[R] Finding unique terms

[roslinazairimah zakaria]

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: roslinazairimah using ump.edu.my <roslinazairimah using ump.edu.my>;
roslinaump using gmail.com <roslinaump using gmail.com>*
Faculty of Industrial Sciences & Technology
University Malaysia Pahang
Lebuhraya Tun Razak, 26300 Gambang, Pahang, Malaysia

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