How to calculate decadal average and percent change in raster stacks?

Oh, I should have said "10-year period", and not "9-year period".

This is because the first year of the decade should be accounted for, i.e. 2010 (including) to 2019.
 Greetings,
 -- Thiago V. dos Santos

PhD student
Land and Atmospheric Science
University of Minnesota

Thanks you all for the responses. Each of them provided very good tips on how to address my problem.

Lo?c, answering your question: the percent change would be within the 9-year period of each decade. Thanks for your response, it was really concise.
Greetings,
-- Thiago V. dos Santos

PhD student
Land and Atmospheric Science
University of Minnesota

Hi Thiago,

This should work for aggregating to decades.

library(raster)
library(lubridate)

# Create the date sequence
idx <- seq(as.Date("2010/1/1"), as.Date("2099/12/31"), by = "year")

# Create raster stack and apply the date
r <- raster(ncol=360, nrow=180)
s <- stack(lapply(1:length(idx), function(x) setValues(r, runif(ncell(r)))))
s <- setZ(s, idx)

# Aggregate to decades
zApply(s, by = function(x) year(x) %/% 10 * 10, fun = mean)


By calculate percent change for each decade, do you mean between decades 
or within?

Cheers,
Lo?c

Dear all,

I am working with yearly climate projections of rainfall that cover the period from 2010 to 2099:

library(raster)

# Create the date sequence
idx <- seq(as.Date("2010/1/1"), as.Date("2099/12/31"), by = "year")

# Create raster stack and apply the date
r <- raster(ncol=360, nrow=180)
s <- stack(lapply(1:length(idx), function(x) setValues(r, runif(ncell(r)))))
s <- setZ(s, idx)
s

Given this raster stack, how can I calculate the average values per decade and percent change for each decade?

I define decades here as 2010-2019, 2020-2029, 2030-2039 and so on until 2090-2099.

I guess the real issue here is how to "split" a raster stack in decades. Any ideas?
Thanks,
  -- Thiago V. dos Santos

PhD student
Land and Atmospheric Science
University of Minnesota

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