[R] aggregate months to years
Oehler, Friderike (AGPP)
Friderike.Oehler at fao.org
Mon Jul 14 14:37:36 CEST 2008
Many thanks for the recent answers to my question about pattern recognition.
The hint to "grep" and the "pattern" argument brought me a big deal forward.
# Now, I have a data frame:
DATE <- c("1930-01-01", "1930-01-01", "1930-02-01", "1931-01-01",
"1931-02-01", "1931-03-01") # almost all months until "1999-12-01". Day is
always 01, the same months actually occur several times.
FREQ <- rep(1,6)
# I can aggregate it like this:
ex <- tapply(ex$FREQ, ex$DATE, sum)
# or use"grep" to extract a single year:
# ex[grep(pattern="^1931", ex$DATE),]
# But how can I aggregate the years such that a barplot would show me the
FREQ per year and not per month?
# Sorry for the bad example, of course my data.frame is much bigger and the
barplot gives me a nice monthly time series of events, but I really only want
the occurrences per year, not per month.
Grateful for your advice!
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