[R] Creating Enumerated Variables

[Gabor Grothendieck]

On Thu, Jul 15, 2010 at 10:45 AM, jdellava <jdellava at 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?
>

The first statement uses ave to create the sequences and the second
statement sorts it:

xx2 <- transform(xx, Count = ave(ID, Age, School, FUN = seq_along))
xx2[order(xx2$Age, xx$School),]