Incorrect month order in zApply function

m <- function(x) ordered(months(x), labels=month.name)
x1 <- zApply(s, by=m, mean) # no name argument.
x1

Hi,

I reworked your example a bit so that it encompasses just one year, and
the value of each layer is the month number for the Z index.  Sure enough,
the mean month number values look like they are mismatched relative to the
layer name.  Example below - sorry about line-wrapping.  Uhoh.

Cheers,
Ben

library(raster)

# Create date sequence
idx <- seq(as.Date("1996/1/1"), as.Date("1996/12/31"), by = "day")

mon_num <- as.numeric(format(idx, "%m"))

# Create raster stack and assign dates
r <- raster(ncol=5, nrow=5)
s <- stack(
    lapply(1:length(idx),
        function(x) setValues(r, rep(mon_num[x],ncell(r)))
        )
    )
s <- setZ(s, idx)

# Calculate monthly average
x <- zApply(s, by=months, mean, name=month.abb[])

x
# class       : RasterBrick
# dimensions  : 5, 5, 25, 12  (nrow, ncol, ncell, nlayers)
# resolution  : 72, 36  (x, y)
# extent      : -180, 180, -90, 90  (xmin, xmax, ymin, ymax)
# coord. ref. : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
# data source : in memory
# names       : April, August, December, February, January, July, June,
March, May, November, October, September
# min values  :     1,      2,        3,        4,       5,    6,    7,
 8,   9,       10,      11,        12
# max values  :     1,      2,        3,        4,       5,    6,    7,
 8,   9,       10,      11,        12

sessionInfo()

R version 3.3.1 (2016-06-21)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.11.6 (El Capitan)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] raster_2.5-8 sp_1.2-3

loaded via a namespace (and not attached):
[1] rgdal_1.1-10    Rcpp_0.12.6     grid_3.3.1      lattice_0.20-33

On Jul 29, 2016, at 3:20 PM, Thiago V. dos Santos via R-sig-Geo <

r-sig-geo at r-project.org> wrote:

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

https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Dsig-2Dgeo&d=CwICAg&c=y2w-uYmhgFWijp_IQN0DhA&r=VXzrzLaooo912e5bVVEO_z5cHQXu_22lipAXBkfCXjM&m=tzdb3kN3Nxjo7NbPkPVqtF269bJen1bf3AzSHEwd7CA&s=zuokuoKIDT6cOaBD2J6ePy1klmf1J3-f3BynP_G5I-g&e=

--
Katherine (Kay) Kilpatrick
University of Miami/RSMAS
Ocean Science Department
Satellite Remote Sensing Laboratory
MSC 231
4600 Rickenbacker Cswy
Miami, Fl
ph: 305-962-3069
kkilpatrick at rsmas.miami.edu

Ben Tupper
Bigelow Laboratory for Ocean Sciences
60 Bigelow Drive, P.O. Box 380
East Boothbay, Maine 04544
http://www.bigelow.org

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