[R] Subset Rasterbrick by time

[Miluji Sb]

Dear David,

Subsetting works but the 'date' information is lost in the new file.

Thanks, Mike. I was not aware of the bug but will work on learning
about (getZ) and (setZ). Thanks again!

Sincerely,

Milu

On Tue, Jun 19, 2018 at 7:32 AM, Michael Sumner <mdsumner using gmail.com> wrote:

>
>
> On Mon, 18 Jun 2018, 22:09 David Winsemius, <dwinsemius using comcast.net>
> wrote:
>
>>
>>
>> > On Jun 18, 2018, at 7:21 AM, Miluji Sb <milujisb using gmail.com> wrote:
>> >
>> > Dear all,
>> >
>> > I have a rasterbrick with the date/time information provided which I
>> would
>> > like to subset by year.
>> >
>> > However, when I use the following code for sub-setting;
>> >
>> > new_brick <- subset(original, which(getZ( original ) >=
>> as.Date("2000-01-01
>> > 10:30:00") & getZ(original ) <= as.Date("2014-12-31 10:30:00")))
>> >
>> > The date/time information seems to be lost.
>> >
>>
>
> This is a bug, I tend to extract (getZ) the dates, do the subset logic on
> both and restore (setZ).
>
> It takes a bit of learning and practice, good luck. I can't expand more at
> the moment. See R-Sig-Geo for more specific discussion forum, and #rstats
> on twitter is really good.
>
> Cheers, Mike
>
>> > Furthermore, the class of the date/time seems to be character;
>> >
>> > ##
>> > class(getZ( original ))
>> > [1] "character"
>> >
>> > Is it possible to convert this string to date before sub-setting or
>> retain
>> > the date/time information after sub-setting?
>>
>> Yes, it is certainly possible, but why bother? R's Comparison operators
>> work on character values so you should be able to do this (if the
>> subsetting is syntactically correct:
>>
>>  new_brick <- subset(original, which(getZ( original ) >= "2000-01-01
>> 10:30:00" & getZ(original ) <= "2014-12-31 10:30:00") )
>>
>>
>> As always if you had presented the output of dput(head(original))
>> assuming that head is a meaningful operation on such an object, the
>> demonstration would have been possible. An alternate would be to offer a
>> library call to a package and then load a relevant example.
>>
>>
>> Best;
>> David
>> >
>> > ### original RasterBrick ###
>> > class       : RasterBrick
>> > dimensions  : 600, 1440, 864000, 11320  (nrow, ncol, ncell, nlayers)
>> > resolution  : 0.25, 0.25  (x, y)
>> > extent      : -180, 180, -60, 90  (xmin, xmax, ymin, ymax)
>> > coord. ref. : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
>> > data source :
>> > /work/mm01117/GLDAS_025_deg/daily/gldas_tavg_tmin_tmax_
>> precip_windspd_sphum_daily_1986_2016.nc4
>> > names       : X1986.01.01.10.30.00, X1986.01.02.10.30.00,
>> > X1986.01.03.10.30.00, X1986.01.04.10.30.00, X1986.01.05.10.30.00,
>> > X1986.01.06.10.30.00, X1986.01.07.10.30.00, X1986.01.08.10.30.00,
>> > X1986.01.09.10.30.00, X1986.01.10.10.30.00, X1986.01.11.10.30.00,
>> > X1986.01.12.10.30.00, X1986.01.13.10.30.00, X1986.01.14.10.30.00,
>> > X1986.01.15.10.30.00, ...
>> > Date/time   : 1986-01-01 10:30:00, 2016-12-31 10:30:00 (min, max)
>> > varname     : v1
>> >
>> > ### new RasterBrick ###
>> > class       : RasterStack
>> > dimensions  : 600, 1440, 864000, 5477  (nrow, ncol, ncell, nlayers)
>> > resolution  : 0.25, 0.25  (x, y)
>> > extent      : -180, 180, -60, 90  (xmin, xmax, ymin, ymax)
>> > coord. ref. : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
>> > names       : X2000.01.01.10.30.00, X2000.01.02.10.30.00,
>> > X2000.01.03.10.30.00, X2000.01.04.10.30.00, X2000.01.05.10.30.00,
>> > X2000.01.06.10.30.00, X2000.01.07.10.30.00, X2000.01.08.10.30.00,
>> > X2000.01.09.10.30.00, X2000.01.10.10.30.00, X2000.01.11.10.30.00,
>> > X2000.01.12.10.30.00, X2000.01.13.10.30.00, X2000.01.14.10.30.00,
>> > X2000.01.15.10.30.00, ...
>> >
>> > Any help will be greatly appreciated.
>> >
>> > Sincerely,
>> >
>> > Milu
>> >
>> >       [[alternative HTML version deleted]]
>> >
>> > ______________________________________________
>> > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> > https://stat.ethz.ch/mailman/listinfo/r-help
>> > PLEASE do read the posting guide http://www.R-project.org/
>> posting-guide.html
>> > and provide commented, minimal, self-contained, reproducible code.
>>
>> ______________________________________________
>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/
>> posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
> --
> Dr. Michael Sumner
> Software and Database Engineer
> Australian Antarctic Division
> 203 Channel Highway
> <https://maps.google.com/?q=203+Channel+Highway+Kingston+Tasmania+7050+Australia&entry=gmail&source=g>
> Kingston Tasmania 7050 Australia
> <https://maps.google.com/?q=203+Channel+Highway+Kingston+Tasmania+7050+Australia&entry=gmail&source=g>
>
>

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