Incorrect month order in zApply function
Thanks everyone for their suggestions. Reordering the output of zApply would be a WRONG solution, because the layers are already ordered from Jan to Dec. It is just the NAMES that are misaligned, which can cause a bit of confusion. I already contacted Robert about this issue and we should see a solution soon. Greetings, -- Thiago V. dos Santos PhD student Land and Atmospheric Science University of Minnesota
On Friday, July 29, 2016 2:09 PM, Kay Kilpatrick <kkilpatrick at rsmas.miami.edu> wrote:
Hi The various Apply functions always return the output in simple alphabetical order when the factor label is a character, regardless of the order of the factor in the calling argument. Ben had a correct solution --- simply reorder the output from Zapply. Alternatively you could use a numeric representation for the month label using by = as.numeric(months(x). The output would then be in increasing numeric order from 1 -12. I do not believe Vijay's suggestion is proper. It does not reorder the output --- instead it changes the label of a given monthly mean eg. The value for Jan. would then be labeled as Apr. k
On 7/28/16 10:52 PM, Thiago V. dos Santos via R-sig-Geo wrote:
Dear all,
I am using the raster package to calculate monthly averages of climatic variables.
Essentially, this is the function I use:
library(raster)
# Create date sequence
idx <- seq(as.Date("1996/1/1"), 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)
# Calculate monthly average
x <- zApply(s, by=months, mean, name=month.abb[])
names(x)
[1] "April" "August" "December" "February" "January" "July" "June"
[8] "March" "May" "November" "October" "September"
getZ(x)
[1] "April" "August" "December" "February" "January" "July" "June"
[8] "March" "May" "November" "October" "September"
The problem here is the output of both names(x) and getZ(x). It looks like a random month order is returned (even though I provide the labels), which makes me confused about the results.
By performing the same calculation in a different software and comparing the results, I came to realize that the order of months for the results by raster should, in fact, be Jan-Feb-Mar-Apr-May-Jun-Jul-Aug-Sep-Oct-Nov-Dec
How can I control the way raster delivers the object names after using zApply, in order to sort the months in the "natural" order?
Greetings, -- Thiago V. dos Santos
PhD student
Land and Atmospheric Science
University of Minnesota
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