GLocation: Classes for fasterRaster sessions, regions, rasters, and...

In adamlilith/fasterRaster: Faster Raster and Spatial Vector Processing Using 'GRASS GIS'

Classes for fasterRaster sessions, regions, rasters, and vectors

Description

The G suite of S4 classes contain pointers to GRASS objects or metadata about the current GRASS session. Most users will manipulate objects using these classes, but do not need to know the details.

• The GLocation class stores information about the GRASS "project"/"location"(see vignette("projects_mapsets", package = "fasterRaster")), and coordinate reference system. Contained by all the rest.

• The GSpatial class contains the GLocation class and stores information about spatial objects (extent, topology) plus the name of the file representing it in GRASS (its source). Contained by GRegion, GRaster, and GVector.

• The GRegion class contains the GSpatial class and stores information about grids (dimensions and resolution). They do have sources, but these are not used (they're always NA). Contained by GRaster. The GRegion corresponds to GRASS "regions", though GRegion objects are not actually pointers to GRASS "region" files (see vignette("regions", package = "fasterRaster")).

• The GRaster class contains the GRegion class and represents rasters. It stores information on number of layers, categories, min/max values, and user-friendly names. Categorical GRasters are associated with a "levels" table for representing categorical data (e.g., wetlands, forest, etc.).

• The GVector class contains the GSpatial class and represents spatial vectors. It may or may not have an associated data.table (i.e., a data.frame), which contains metadata about each geometry in the vector.

Value

An object of class GLocation, GSpatial, GRegion, GRaster, or GVector.

Slots

location

Character (all classes): The GRASS "project"/"location" of the object. The default value is default. Can be obtained using the hidden function .location(). See vignette("projects_mapsets", package = "fasterRaster").

mapset

Character (all classes): The GRASS "mapset". Default value is PERMANENT. Typically hidden to users. Can be obtained using the hidden function .mapset(). See vignette("projects_mapsets", package = "fasterRaster").

workDir

Character (all classes): Directory in which GRASS stores files.

topology

Character (GSpatial objects, including GRegions, GRasters, and GVectors): Valid values are ⁠2D⁠ (2-dimensional–most rasters and vectors) or ⁠3D⁠ (3-dimensional–e.g., LIDAR data). Can be obtained using topology().

sources

Character (GRasters and GVectors): Name of the object in GRASS. These are typically made on-the-fly and provide the pointer to the object from R to GRASS. Changing them manually will break the connection. Can be obtained using sources().

names

Character (GRasters only): Name of a raster or each raster layer in. Can be obtained using names().

crs

Character (all classes): Coordinate reference systems string (preferably in WKT2 format). Can be obtained using crs() or st_crs().

projection

Character: The GRASS "projection" for a GRaster or GVector. Can be obtained using .projection().

dimensions

Dimensions:

• GRegions and GRasters: Vector of three integers indicating number of rows, columns, and depths (for 3D objects). Can be obtained using dim(), plus nrow(), ncol(), and ndepth().

• GVectorss: Vector of two integers indicating number of geometries and number of fields. Can be obtained using dim(), plus nrow() and ncol().

extent

Numeric vector with four values (GSpatial objects, including GRegions, GRasters, and GVectors): Extent of the object listed in order from westernmost longitude, easternmost longitude, southernmost latitude, northernmost latitude. Can be obtained using ext().

zextent

Numeric (GSpatial objects, including GRegions, GRasters, and GVectors): Bottom- and top-most extents of 3D GRasters and GVectors. Can be obtained using zext().

geometry

Character (GVectorss): Either points, lines, or polygons. Can be obtained using geomtype().

nLayers

Integer (GRasters): Number of layers ("stacked" rasters–different from number of depths of 3D rasters). Can be obtained using nlyr().

nGeometries

Integer (GVectors): Number of features (points, lines, or polygons). Can be obtained using nrow().

datatypeGRASS

Character (GRasters): Type of data stored in a raster, as interpreted by GRASS. This is either CELL (integers), FCELL (floating-point values), or DCELL (double-values). Can be obtained using datatype().

resolution

Vector of two numeric values (GRegions, including GRasters): Size of a raster cell in the east-west direction and in the north-south direction. Can be obtained using res() and res3d().

minVal,maxVal

Numeric (GRasters): Minimum and maximum value across all cells. Can be obtained using minmax().

activeCat

Integer (GRasters): Column index of the category labels. Must be >0. Note that from the user's standpoint, 1 is subtracted from this number. So a value if ⁠@activeCat⁠ is 2, then the user would see "1" when printed. Can be obtained using activeCat().

levels

List of data.tables (GRasters): Tables for categorical rasters. If a raster is not categorical, the data.table is NULL, as in data.table(NULL). Can be obtained using levels() or cats().

table

data.table (GVectors): Table with metadata, one row per geometry (point, line, or plane). If no table is associated with the vector, this must be data.table(NULL). The column with the category value is given in ⁠@catName⁠.

catName

Character (GVectors): Name of the column in the vector's database that contains category values (integers).

adamlilith/fasterRaster documentation built on Oct. 26, 2024, 4:06 p.m.