Map: location coordinates (id, x, y, mark)

.map_coord() defines coordinates and weights (marks) for utilisation distribution (UD) estimation.

Usage

.map_coord(.map, .coord, .discretise)

.map_coord.SpatRaster(.map)

.map_coord.dt(.map, .coord, .discretise)

Arguments

.map

The terra::SpatRaster used to represent the UD. This can be NULL if .coord is provided and .discretise = FALSE.

.coord

A matrix, data.frame or data.table::data.table with x and y coordinates, in columns named x and y or cell_x and cell_y (see Details). (.coord is coerced to a data.table::data.table.) Additional columns (timestep and mark), as supported by .map_mark() are permitted. Other columns are ignored.

.discretise

A logical variable that defines whether or not to discretise coordinates (i.e., redefine coordinates on .map). This is necessarily TRUE in the wrapper function map_pou() but optional for map_dens().

Value

The function returns a data.table::data.table with four columns:

• id—a vector of coordinate IDs (if .discretise = TRUE, id represents grid cells on .map);

• x,y—numeric vectors that define coordinates (if .discretise = TRUE, x and y represent cell coordinates on .map);

• mark—a numeric vector of weights, normalised to sum to one;

Details

.map_coord() function defines a data.table::data.table that includes coordinate IDs (id), coordinates (x and y) and associated weights (mark) for UD estimation. The function wraps .map_coord.SpatRaster() and .map_coord.dt().

• If .coord is NULL, .map_coord.SpatRaster() is used. This function extracts a data.table::data.table of coordinates from .map (in non NA regions) via terra::as.data.frame(..., na.rm = TRUE). The values on .map are taken as weights and must sum to one.

• If .coord is supplied, .map_coord.dt() is used. x and y and/or cell_x and cell_y columns are expected. If .discretise = TRUE, cell_x and cell_y are used preferentially. Irrespective of whether or not x and y or cell_x and cell_y are specified, coordinates are redefined on .map and coordinate IDs are defined as grid cell IDs on .map. If .discretise = FALSE, x and y coordinates are used preferentially. Coordinates remain unchanged and IDs are defined from the set of unique coordinate pairs. For each ID, weights are calculated by .map_mark().

See also

.map_coord() is used by map_pou() and map_dens().

Author

Edward Lavender