Message-ID: <BANLkTi=iiTcm9_R1FtHmT=QaB+XJTZWvkA@mail.gmail.com>
Date: 2011-04-04T19:54:34Z
From: Gabor Grothendieck
Subject: zoo:rollapply by multiple grouping factors
In-Reply-To: <4D9A1EA9.1010203@ucsc.edu>
On Mon, Apr 4, 2011 at 3:40 PM, Mark Novak <mnovak1 at ucsc.edu> wrote:
> Thank you very much Gabor! ?It looks like that's gonna work wonderfully. ?I
> didn't even know 'ave' existed.
>
> For others out there: ?I only needed to add a comma: ? dat[,c("Site",
> "Plot", "Sp")]
Actually, if dd is a data frame dd[, ix] and dd[ix] give the same result. e.g.
> dd <- data.frame(a = 1:3, b = 11:13, c = 21:23)
> identical(dd[, c("b", "c")], dd[c("b", "c")])
[1] TRUE
> Small follow up Q: ?Is there any reason to use 'aggregate' vs. 'ave' in
> general?
aggregate reduces the data to fewer rows. ave adds a potentially
additional column to the original data.
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