[R] Simple programming question

[Gabor Grothendieck]

Try this.  f assigns 1, 2 and 3 to the highest, second highest and third highest
within a category.  ave applies f to each category.  Finally we convert it to a
factor.

f <- function(x) 4 - pmin(3, match(x, sort(x, decreasing = TRUE)))
factor(ave(dfr$var3, dfr$categ, FUN = f), lab = c("low", "mid", "high"))



On 5/18/07, Lauri Nikkinen <lauri.nikkinen at iki.fi> wrote:
> Hi R-users,
>
> I have a simple question for R heavy users. If I have a data frame like this
>
>
> dfr <- data.frame(id=1:16, categ=rep(LETTERS[1:4], 4),
> var3=c(8,7,6,6,5,4,5,4,3,4,3,2,3,2,1,1))
> dfr <- dfr[order(dfr$categ),]
>
> and I want to score values or points in variable named "var3" following this
> kind of logic:
>
> 1. the highest value of var3 within category (variable named "categ") ->
> "high"
> 2. the second highest value -> "mid"
> 3. lowest value -> "low"
>
> This would be the output of this reasoning:
>
> dfr$score <-
> factor(c("high","mid","low","low","high","mid","mid","low","high","mid","low","low","high","mid","low","low"))
> dfr
>
> The question is how I do this programmatically in R (i.e. if I have 2000
> rows in my dfr)?
>
> I appreciate your help!
>
> Cheers,
> Lauri
>
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