Dear all,
I am using the raster package to calculate seasonal averages of climatic
variables. I usually use zApply to perform temporal calculations on gridded
time series.
However, this time I need to calculate seasonal averages according to the
meteorological nomenclature, with DJF (=winter in the southern hemisphere:
December, January, February), MAM, JJA, and SON. It is similar to zoo's
yearqtr, but with a offset of -1 month on each quarter.
That means that December values comes from the previous year.
This is a typical raster I work with:
library(raster)
# Create date sequence
idx <- seq(as.Date("2001/1/1"), as.Date("2010/12/31"), by = "day")
# Create raster stack and assign dates
r <- raster(ncol=5, nrow=5)
s <- stack(lapply(1:length(idx), function(x) setValues(r, runif(ncell(r)))))
s <- setZ(s, idx)
On a raster stack like this, what would be the best strategy to calculate
"meteorological" seasonal means?
Thanks in advance,
-- Thiago V. dos Santos
PhD student
Land and Atmospheric Science
University of Minnesota
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