[R-sig-Geo] How to perform cross-year date operations on rasters?

[Thiago V. dos Santos]

Dear all,

Consider that I have a raster stack with daily values. How can I perform date operations covering a time interval that crosses years?

For example, I want to sum the values from every october-to-january period in this sample raster:

library(raster)

# Create a rasterStack similar to cmip5 - same dimensions and layer names
r <- raster(ncol=180, nrow=90)
s <- stack(lapply(1:1825, function(x) setValues(r, runif(ncell(r)))))

# Apply time stamps to raster
#x <- as.Date(c("2010-01-01","2014-12-31"),format="%Y-%m-%d") 
#difftime(x[2], x[1], units="days") 
idx <- seq(as.Date("2010/1/1"), by = "day", length.out = 1825)
s <- setZ(s, idx)
s


 Thanks in advance,
 -- Thiago V. dos Santos

PhD student
Land and Atmospheric Science
University of Minnesota