[R] Finding unique terms

[Jeff Newmiller]

You said "add up"... so you did not mean to say that? Denes computed the mean...

On October 11, 2018 3:56:23 PM PDT, roslinazairimah zakaria <roslinaump using gmail.com> wrote:
>Hi Denes,
>
>It works perfectly as I want!
>
>Thanks a lot.
>
>On Fri, Oct 12, 2018 at 6:29 AM Dénes Tóth <toth.denes using 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.
>> >
>>

-- 
Sent from my phone. Please excuse my brevity.