subsets GDAL objects, returning a SpatialGridDataFrame object

Methods

"["

signature(.Object = "GDALReadOnlyDataset"): requires package sp; selects rows and columns, and returns an object of class SpatialGridDataFrame if the grid is not rotated, or else of class SpatialPointsDataFrame. Any arguments passed to getRasterData (or in case of rotation getRasterTable) may be passed as named arguments; the first three unnamed arguments are row,col,band

Details

The [ method subsets a GDAL data set, returning a SpatialGridDataFrame object. Reading is done on the GDAL side, and only the subset requested is ever read into memory.

Further named arguments to [ are to either getRasterTable or getRasterData:

as.is

see getRasterData

interleave

see getRasterData

output.dim

see getRasterData

the other arguments, offset and region.dim are derived from row/column selection values.

An GDALReadOnlyDataset object can be coerced directly to a SpatialGridDataFrame

Author

Edzer Pebesma

See also

Examples

library(grid) logo <- system.file("pictures/logo.jpg", package="rgdal")[1] x <- new("GDALReadOnlyDataset", logo) dim(x)
#> [1] 175 200
x.sp = x[20:50, 20:50]
#> Warning: GeoTransform values not available
class(x.sp)
#> [1] "SpatialGridDataFrame" #> attr(,"package") #> [1] "sp"
summary(x.sp)
#> Object of class SpatialGridDataFrame #> Coordinates: #> min max #> x 19 50 #> y 125 156 #> Is projected: NA #> proj4string : [NA] #> Grid attributes: #> cellcentre.offset cellsize cells.dim #> x 19.5 1 31 #> y 125.5 1 31 #> Data attributes: #> band1 #> Min. :192.0 #> 1st Qu.:200.0 #> Median :204.0 #> Mean :224.1 #> 3rd Qu.:255.0 #> Max. :255.0
spplot(x.sp)
GDAL.close(x) logo <- system.file("pictures/Rlogo.jpg", package="rgdal")[1] x.gdal <- new("GDALReadOnlyDataset", logo) x = x.gdal[,,3]
#> Warning: GeoTransform values not available
dim(x)
#> [1] 35000 1
#> Object of class SpatialGridDataFrame #> Coordinates: #> min max #> x 0 200 #> y 0 175 #> Is projected: NA #> proj4string : [NA] #> Grid attributes: #> cellcentre.offset cellsize cells.dim #> x 0.5 1 200 #> y 0.5 1 175 #> Data attributes: #> band1 #> Min. :127.0 #> 1st Qu.:188.0 #> Median :255.0 #> Mean :224.6 #> 3rd Qu.:255.0 #> Max. :255.0
spplot(x)
spplot(x.gdal[])
#> Warning: GeoTransform values not available
GDAL.close(x.gdal) logo <- system.file("pictures/Rlogo.jpg", package="rgdal")[1] x.gdal <- new("GDALReadOnlyDataset", logo) x.as <- as(x.gdal, "SpatialGridDataFrame")
#> Warning: GeoTransform values not available
GDAL.close(x.gdal) summary(x.as)
#> Object of class SpatialGridDataFrame #> Coordinates: #> min max #> x 0 200 #> y 0 175 #> Is projected: NA #> proj4string : [NA] #> Grid attributes: #> cellcentre.offset cellsize cells.dim #> x 0.5 1 200 #> y 0.5 1 175 #> Data attributes: #> band1 band2 band3 #> Min. : 8.0 Min. : 75.0 Min. :127.0 #> 1st Qu.:162.0 1st Qu.:163.0 1st Qu.:188.0 #> Median :255.0 Median :255.0 Median :255.0 #> Mean :192.4 Mean :206.7 Mean :224.6 #> 3rd Qu.:255.0 3rd Qu.:255.0 3rd Qu.:255.0 #> Max. :255.0 Max. :255.0 Max. :255.0