[R] Subset Rasterbrick by time

[David Winsemius]

> 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.
> 
> 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
> 
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> 
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