raster

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Create a RasterLayer object

Methods to create a RasterLayer object. RasterLayer objects can be created from scratch, a file, an Extent object, a matrix, an 'image' object, or from a Raster*, Spatial*, im (spatstat) asc, kasc (adehabitat*), grf (geoR) or kde object.

In many cases, e.g. when a RasterLayer is created from a file, it does (initially) not contain any cell (pixel) values in (RAM) memory, it only has the parameters that describe the RasterLayer. You can access cell-values with getValues, extract and related functions. You can assign new values with setValues and with replacement.

For an overview of the functions in the raster package have a look here: raster-package.

Keywords
methods, spatial
Usage
"raster"(x, band=1, ...)
"raster"(x)
"raster"(x, layer=0)
"raster"(x, layer=0)
"raster"(nrows=180, ncols=360, xmn=-180, xmx=180, ymn=-90, ymx=90, crs, ext, resolution, vals=NULL)
"raster"(x, nrows=10, ncols=10, crs=NA, ...)
"raster"(x, xmn=0, xmx=1, ymn=0, ymx=1, crs=NA, template=NULL)
"raster"(x, xmn=0, xmx=1, ymn=0, ymx=1, crs=NA, template=NULL)
"raster"(x, origin, ...)
"raster"(x, layer=1, values=TRUE)
"raster"(x, layer=1, values=TRUE)
Arguments
x
filename (character), Extent, Raster*, SpatialPixels*, SpatialGrid*, object, 'image', matrix, im, or missing. Supported file types are the 'native' raster package format and those that can be read via rgdal (see readGDAL
band
integer. The layer to use in a multi-layer file
...
Additional arguments, see Details
layer
integer. The layer (variable) to use in a multi-layer file, or the layer to extract from a RasterStack/Brick or SpatialPixelsDataFrame or SpatialGridDataFrame. An empty RasterLayer (no associated values) is returned if layer=0
values
logical. If TRUE, the cell values of 'x' are copied to the RasterLayer object that is returned
nrows
integer > 0. Number of rows
ncols
integer > 0. Number of columns
xmn
minimum x coordinate (left border)
xmx
maximum x coordinate (right border)
ymn
minimum y coordinate (bottom border)
ymx
maximum y coordinate (top border)
ext
object of class Extent. If present, the arguments xmn, xmx, ymn and ynx are ignored
crs
character or object of class CRS. PROJ.4 type description of a Coordinate Reference System (map projection). If this argument is missing, and the x coordinates are withing -360 .. 360 and the y coordinates are within -90 .. 90, "+proj=longlat +datum=WGS84" is used. Also see under Details if x is a character (filename)
resolution
numeric vector of length 1 or 2 to set the resolution (see res). If this argument is used, arguments ncols and nrows are ignored
vals
optional. Values for the new RasterLayer. Accepted formats are as for setValues
origin
minimum y coordinate (bottom border)
template
Raster* or Extent object used to set the extent (and CRS in case of a Raster* object). If not NULL, arguments xmn, xmx, ymn, ymx and crs (unless template is an Extent object) are ignored
Details

If x is a filename, the following additional variables are recognized:

sub: positive integer. Subdataset number for a file with subdatasets

native: logical. Default is FALSE except when package rgdal is missing. If TRUE, reading and writing of IDRISI, BIL, BSQ, BIP, SAGA, and Arc ASCII files is done with native (raster package) drivers, rather then via rgdal. 'raster' and netcdf format files are always read with native drivers.

RAT: logical. The default is TRUE, in which case a raster attribute table is created for files that have one

offset: integer. To indicate the number of header rows on non-standard ascii files (rarely useful; use with caution)

crs: character. PROJ.4 string to set the CRS. Ignored when the file provides a CRS description that can be interpreted.

If x represents a NetCDF file, the following additional variable is recognized:

varname: character. The variable name, such as 'tasmax' or 'pr'. If not supplied and the file has multiple variables are a guess will be made (and reported)

lvar: integer > 0 (default=3). To select the 'level variable' (3rd dimension variable) to use, if the file has 4 dimensions (e.g. depth instead of time)

level: integer > 0 (default=1). To select the 'level' (4th dimension variable) to use, if the file has 4 dimensions, e.g. to create a RasterBrick of weather over time at a certain height.

To use NetCDF files the ncdf4 package needs to be available. It is assumed that these files follow, or are compatible with, the CF-1 convention (The GMT format may also work). If the ncdf file does not have a standard extension (which is used to recognize the file format), you can use argument ncdf=TRUE to indicate the format.

If x is a Spatial or an Extent object, additional arguments are for the method with signature 'missing'

Value

RasterLayer

See Also

stack, brick

Aliases
  • raster
  • raster,missing-method
  • raster,character-method
  • raster,Extent-method
  • raster,BasicRaster-method
  • raster,RasterLayer-method
  • raster,RasterLayerSparse-method
  • raster,RasterStack-method
  • raster,RasterBrick-method
  • raster,Spatial-method
  • raster,SpatialGrid-method
  • raster,SpatialPixels-method
  • raster,matrix-method
  • raster,big.matrix-method
  • raster,list-method
  • raster,im-method
  • raster,asc-method
  • raster,kasc-method
  • raster,kde-method
  • raster,grf-method
  • raster,GridTopology-method
Examples
# Create a RasterLayer object from a file
#   N.B.: For your own files, omit the 'system.file' and 'package="raster"' bits
#   these are just to get the path to files installed with the package

f <- system.file("external/test.grd", package="raster")
f
r <- raster(f)

logo <- raster(system.file("external/rlogo.grd", package="raster")) 


#from scratch
r1 <- raster(nrows=108, ncols=21, xmn=0, xmx=10)

#from an Extent object
e <- extent(r)
r2 <- raster(e)

#from another Raster* object
r3 <- raster(r)
s <- stack(r, r, r)
r4 <- raster(s)
r5 <- raster(s, 3)


## Not run: 
# # from NSIDC sea ice concentration file
# baseurl <- "ftp://sidads.colorado.edu/pub/DATASETS/"
# # southern hemisphere
# f1 <- paste(baseurl, 
#  "nsidc0051_gsfc_nasateam_seaice/final-gsfc/south/daily/2013/nt_20130114_f17_v01_s.bin",
#  sep='')
# # or northern hemisphere
# f2 <- paste(baseurl, 
#  "nsidc0051_gsfc_nasateam_seaice/final-gsfc/north/daily/2013/nt_20130105_f17_v01_n.bin",
#  sep='')
#      
# if (!file.exists(basename(f1))) download.file(f1, basename(f1), mode = "wb")
# ice1 <- raster(basename(f1))
# 
# if (!file.exists(basename(f2))) download.file(f2, basename(f2), mode = "wb")
# ice2 <- raster(basename(f2))
#      
# ## End(Not run)
Documentation reproduced from package raster, version 2.5-8, License: GPL (>= 3)

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