Georg Hoermann [mailto:[EMAIL PROTECTED] wrote:
> www.hydrology.uni-kiel.de/~schorsch/statistik/erle_stat.csv ...
contains a 10 year dataset.
> We often need cumulative *annual* sums (sunshine, precipitation), i.e.
the sum must reset to 0
> at the beginning of the year. I know of cumsum(), but I do not now how
to split the dataset
> automagically into annual pieces so I can cumsum() every year
separately.
Several replies have been given using tapply/aggregate/split; here is a
more primitive approach.
I do the cumsum once for the series, and call it "x". Then I subtract
from x the value of x on 12/31
of the prior year:
R> y <- read.csv("erle_stat.csv", as.is=TRUE)
R> year <- substring(y$DATUM, 7)
R> x <- cumsum(y$Peff)
R> y$cumPeff <- x - c(0,x)[match(year, year)]
-- David Brahm ([EMAIL PROTECTED])
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