dataframe manipulation

Hi,
Try:
?d[match(unique(d$fac),d$fac),]
A.K.

Suppose I have a dataframe defined as

? ?  L3 <- LETTERS[1:3]
? ?  (d <- data.frame(cbind(x = 1, y = 1:10), fac = sample(L3, 10, replace
= TRUE)))

?  x? y fac
1? 1? 1?  C
2? 1? 2?  A
3? 1? 3?  B
4? 1? 4?  C
5? 1? 5?  B
6? 1? 6?  B
7? 1? 7?  A
8? 1? 8?  A
9? 1? 9?  B
10 1 10?  A

I want to extract those rows that are the first occurrences for each level
of factor 'fac', which are basically the first three rows above. How can I
achieve that? The real dataframe is more complicated than the example
above, and I can't simply list all the levels of factor 'fac' by
exhaustibly listing all the levels like the following

d[d$fac=='A' | d$fac=='B' | d$fac=='C', ]

Thanks,
Gang

??? [[alternative HTML version deleted]]

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