[R-sig-Geo] Subsetting Raster Time Series

[Srinivas V]

Thanks the nested approach worked perfectly.
Regards
Srinivas

  

On Tuesday 26 August 2014 05:24 PM, Dutrieux, Loic wrote:
> Hi Srinivas,
>
> You can access the time dimension of these raster object using the getZ and setZ functions; both from the raster package (avoid when possible accessing objects' slots by using @). Following that it is mostly vector arithmetic, which can be achieved in several ways.
>
> Using the example in the help of getZ.
>
> library(raster)
> # Create a rasterStack object with time written to z dimension.
> r <- raster(ncol=10, nrow=10)
> s <- stack(lapply(1:3, function(x) setValues(r, runif(ncell(r)))))
> s <- setZ(s, as.Date('2000-1-1') + 0:2)
> s
>
> # Extract time vector
> time <- getZ(s)
> # You can get the indices which fit your subset criteria using which() and inject them into raster::subset()
> id <- which(time < as.Date('2000-1-3'))
> subset(s, id)
>
> # Nested
> subset(s, which(getZ(s) < as.Date('2000-1-3')))
>
> Best regards,
>
> --
> Loïc Dutrieux
> Laboratory of Geo-Information sciences and remote sensing
> Wageningen University
> The Netherlands
>
>
>
>
> -----Original Message-----
> From: r-sig-geo-bounces at r-project.org [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of Srinivas V
> Sent: Tuesday, August 26, 2014 11:56
> To: r-sig-geo at r-project.org
> Subject: [R-sig-Geo] Subsetting Raster Time Series
>
> Hi,
>
> I would like to subset the CRU dataset to a particular time period
> (1980-2013) is there an option to do this within package raster? I can manually specifiy the layers to drop, but I would like to drop them based on a time period. I'm doing this to ensure two datasets are of the same time period.
>
> I would appreciate any advice on dealing with this issue. Thanks!
>
> library(raster)
> library(rgdal)
> library(ncdf)
> library(zoo)
>
> temp<-brick("/media/data/data_cru/tmp/cru_ts3.22.1901.2013.tmp.dat.nc")
> temp
> temp at z
>
> output
> +++++
>   > temp
> class       : RasterBrick
> dimensions  : 360, 720, 259200, 1356  (nrow, ncol, ncell, nlayers) resolution  : 0.5, 0.5  (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 : /media/data/data_cru/tmp/cru_ts3.22.1901.2013.tmp.dat.nc
> names       : X1901.01.16, X1901.02.15, X1901.03.16, X1901.04.16,
> X1901.05.16, X1901.06.16, X1901.07.16, X1901.08.16, X1901.09.16, X1901.10.16, X1901.11.16, X1901.12.16, X1902.01.16, X1902.02.15, X1902.03.16, ...
> Date        : 1901-01-16, 2013-12-16 (min, max)
> varname     : tmp
>
>   > temp at z
> $Date
>    [1] "1901-01-16" "1901-02-15" "1901-03-16" "1901-04-16" "1901-05-16"
> "1901-06-16" "1901-07-16" "1901-08-16" "1901-09-16" "1901-10-16"
>
> [1351] "2013-07-16" "2013-08-16" "2013-09-16" "2013-10-16" "2013-11-16"
> "2013-12-16"
>
>
>


	[[alternative HTML version deleted]]