terra (version 1.1-4)

rast: Create a SpatRaster

Description

Methods to create a SpatRaster. These objects can be created from scratch or from a file.

A SpatRaster represents a spatially referenced surface divided into three dimensional cells (rows, columns, and layers).

When a SpatRaster is created from a file, it does not load the cell (pixel) values into memory (RAM). It only reads the basic parameters that describe the SpatRaster such as the number of rows and columns and the coordinate reference system. The actual values will be read, perhaps in chunks -- to avoid memory overflows -- as needed.

Usage

# S4 method for character
rast(x, subds=0)
# S4 method for missing
rast(x, nrows=180, ncols=360, nlyrs=1, xmin=-180, xmax=180, 
          ymin=-90, ymax=90, crs, extent, resolution, vals)
# S4 method for SpatRaster
rast(x, nlyrs=nlyr(x)) 
# S4 method for matrix
rast(x, type="", crs="", digits=6)
# S4 method for list
rast(x)
# S4 method for SpatRasterDataset
rast(x)
# S4 method for SpatVector
rast(x, ...)
									  
# S4 method for SpatExtent
rast(x, ...)

Arguments

x

filename (character), missing, SpatRaster, SpatRasterDataset, SpatExtent, SpatVector, matrix, array, list of SpatRaster objects. For other types it will be attempted to create a SpatRaster via (`as(x, "SpatRaster")`

subds

positive integer or character to select a subdataset. If zero or "", all subdatasets are returned (if possible)

nrows

positive integer. Number of rows

ncols

positive integer. Number of columns

nlyrs

positive integer. Number of layers

xmin

minimum x coordinate (left border)

xmax

maximum x coordinate (right border)

ymin

minimum y coordinate (bottom border)

ymax

maximum y coordinate (top border)

crs

character. PROJ.4 type description of a Coordinate Reference System (map projection). If this argument is missing, and the x coordinates are within -360 .. 360 and the y coordinates are within -90 .. 90, "+proj=longlat +datum=WGS84" is used

extent

object of class SpatExtent. If present, the arguments xmin, xmax, ymin and ymax are ignored

resolution

numeric vector of length 1 or 2 to set the resolution (see res). If this argument is used, arguments ncol and nrow are ignored

vals

numeric. An optional vector with cell values (if fewer values are provided, these are recycled to reach the number of cells)

type

character. If the value is not "xyz", the raster has the same number of rows and colums as the matrix. If the value is "xyz", the matrix must have at least two columns, the first with x (or longitude) and the second with y (or latitude) coordinates that represent the centers of raster cells. The additional columns are the values associated with the raster cells.

digits

integer to set the precision for detecting whether points are on a regular grid (a low number of digits is a low precision). Only used when type="xyz"

...

additional arguments, in some cases passed on to the rast,missing-method

Value

SpatRaster

Details

The files are opened and read via GDAL. GDAL guesses the file format from the name, and/or else tries reading it with different "drivers" untill it succeeds. In very few cases this may cause a file to be opened with wrong driver, and some information may be lost (for example because of opening a netCDF file with the HDF5 driver. You can avoid that by prepending the driver name to the filename like this: rast('NETCDF:"filename.ncdf"')

Examples

# NOT RUN {
# Create a SpatRaster from scratch
x <- rast(nrow=108, ncol=21, xmin=0, xmax=10)

# Create a SpatRaster from a file
f <- system.file("ex/elev.tif", package="terra")
r <- rast(f)

s <- rast(system.file("ex/logo.tif", package="terra"))   

# Create a skeleton with no associated cell values
rast(s)
# }