Hi:
I sincerely hope there's an easier way, but one method to get this is as
follows,
with d as the data frame name of your test data:
d <- d[order(with(d, Age, School, rev(Grade))), ]
d$Count <- do.call(c, mapply(seq, 1, as.vector(t(with(d, table(Age,
School))))))
d
> d
ID Age School Grade Count
1 1 10 1 98 1
3 3 10 1 92 2
7 7 10 1 80 3
8 8 10 1 79 4
2 2 10 2 97 1
4 4 11 1 90 1
5 5 11 1 80 2
6 6 11 2 70 1
9 9 11 2 70 2
The code to get the count is a little convoluted:
- first, find the frequency table of Age and School, transpose it and
then unlist into a vector
- use mapply to generate a sequence for each group from 1 up to its
group count; mapply() is necessary to use the counts as a vector argument.
This returns a list of sequences.
- do.call() applies a function (here, c) to an input list, yielding the
vector of groupwise indices we wanted. Basically, it flattens the list. This
is what we assign to d$Count.
Side note: I didn't get the correct ordering the first time, but I did the
second time (2.11.1 64bit, Windows 7).
HTH,
Dennis
On Thu, Jul 15, 2010 at 7:45 AM, jdellava <jdell...@vcu.edu> wrote:
>
> Hi,
>
> I am trying to create a variable counting the number of individuals based
> on
> two variables. I am able to do it or one variable, but not two. In SAS I
> was
> able to sort by two variables and use a first. statement to create the
> counts based on both. Here is an example:
>
> What I have
> ID Age School Grade
> 1 10 1 98
> 2 10 2 97
> 3 10 1 92
> 4 11 1 90
> 5 11 1 80
> 6 11 2 70
> 7 10 1 80
> 8 10 1 79
> 9 11 2 70
>
> What I need
> ID Age School Grade School Count
> 1 10 1 98 1
> 3 10 1 92 2
> 7 10 1 80 3
> 8 10 1 79 4
> 2 10 2 97 1
> 4 11 1 90 1
> 5 11 1 80 2
> 6 11 2 70 1
> 9 11 2 70 2
>
> I want to create counts of individuals age 10 in school 1 then age 10 in
> school two (the what I need set)
>
> Anyway to do this?
>
> Thank you.
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/Creating-Enumerated-Variables-tp2290262p2290262.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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