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Methods to create a SpatRaster. These objects can be created from scratch, from a filename, or from another object.

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 parameters that describe the geometry of the SpatRaster, such as the number of rows and columns and the coordinate reference system. The actual values will be read when needed.

Usage

# S4 method for character
rast(x, subds=0, lyrs=NULL, drivers=NULL, opts=NULL, 
      win=NULL, snap="near", vsi=FALSE, raw=FALSE)

# S4 method for missing
rast(x, nrows=180, ncols=360, nlyrs=1, xmin=-180, xmax=180, 
          ymin=-90, ymax=90, crs, extent, resolution, vals, names, time, units)

# S4 method for SpatRaster
rast(x, nlyrs=nlyr(x), names, vals, keeptime=TRUE, 
      keepunits=FALSE, props=FALSE, tags=FALSE) 

# S4 method for matrix
rast(x, type="", crs="", digits=6, extent=NULL)

# S4 method for data.frame
rast(x, type="xyz", crs="", digits=6, extent=NULL)

# S4 method for array
rast(x, crs="", extent=NULL)

# S4 method for list
rast(x, warn=TRUE)

# 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 SpatRasters. For other types it will be attempted to create a SpatRaster via (`as(x, "SpatRaster")`

subds

positive integer or character to select a sub-dataset. If zero or "", all sub-datasets are returned (if possible)

lyrs

positive integer or character to select a subset of layers (a.k.a. "bands")

drivers

character. GDAL drivers to consider

opts

character. GDAL dataset open options

win

SpatExtent to set a window (area of interest)

snap

character. One of "near", "in", or "out", to indicate how the extent of window should be "snapped" to x

vsi

logical. If TRUE, "\vsicurl\" is prepended to filenames that start with "http"

raw

logical. If TRUE, scale and offset values are ignored. See scoff to get these parameters

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. Description of the Coordinate Reference System (map projection) in PROJ.4, WKT or authority:code notation. See crs. If this argument is missing, and the x coordinates are within -360 .. 360 and the y coordinates are within -90 .. 90, longitude/latitude is assigned

keeptime

logical. If FALSE the time stamps are discarded

keepunits

logical. If FALSE the layer units are discarded

props

logical. If TRUE the properties (categories and color-table) are kept

tags

logical. If TRUE the user specified metadata tags are kept (see metags).

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 spatial resolution (see res). If this argument is used, arguments ncols and nrows are ignored

vals

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

names

character. An optional vector with layer names (must match the number of layers)

time

time or date stamps for each layer

units

character. units for each layer

type

character. If the value is "xyz", the matrix or data.frame x 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. If the value is "xylz", x must have four columns with the third representing the layer and the fourth the cell values. If the value is "", the resulting SpatRaster will have the same number of rows and columns as x.

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"

warn

logical. If TRUE, a warnings about empty rasters may be emitted

...

additional arguments passed on to the rast,missing-method

Value

SpatRaster

Details

Files are read with the GDAL library. GDAL guesses the file format from the name, and/or tries reading it with different "drivers" (see gdal) until it succeeds. In very few cases this may cause a file to be opened with the wrong driver, and some information may be lost. For example, when a netCDF file is opened with the HDF5 driver. You can avoid that by using argument rast("filename.ncdf", drivers="NETCDF")

These classes hold a C++ pointer to the data "reference class" and that creates some limitations. They cannot be recovered from a saved R session either or directly passed to nodes on a computer cluster. Generally, you should use writeRaster to save SpatRaster objects to disk (and pass a filename or cell values of cluster nodes). Also see wrap.

See also

sds to create a SpatRasterDataset (4 dimensions) and vect for vector (points, lines, polygons) data

Examples

# Create a SpatRaster from scratch
x <- rast(nrows=108, ncols=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)
#> class       : SpatRaster 
#> dimensions  : 77, 101, 3  (nrow, ncol, nlyr)
#> resolution  : 1, 1  (x, y)
#> extent      : 0, 101, 0, 77  (xmin, xmax, ymin, ymax)
#> coord. ref. : Cartesian (Meter) 

# from a matrix 
m <- matrix(1:25, nrow=5, ncol=5)
rm <- rast(m)

# from a "xyz" data.frame
d <- as.data.frame(rm, xy=TRUE)
head(d)
#>     x   y lyr.1
#> 1 0.5 4.5     1
#> 2 1.5 4.5     6
#> 3 2.5 4.5    11
#> 4 3.5 4.5    16
#> 5 4.5 4.5    21
#> 6 0.5 3.5     2
rast(d, type="xyz")
#> class       : SpatRaster 
#> dimensions  : 5, 5, 1  (nrow, ncol, nlyr)
#> resolution  : 1, 1  (x, y)
#> extent      : 0, 5, 0, 5  (xmin, xmax, ymin, ymax)
#> coord. ref. :  
#> source(s)   : memory
#> name        : lyr.1 
#> min value   :     1 
#> max value   :    25