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Determine if points are between BirdFlow cells

Source: R/is_between.R
is_between.Rd

This internal function is used to create a betweenness array with dimensions n_active(bf), n_active(bf), and length(points). The first two dimensions from and to cells of possible connections between pairs of locations within the BirdFlow model and both n_active() elements. The third dimension represents points that might be between each connection. Cell values are TRUE if the point is between the associated model cells. Specifically, if the point is within radius meters (along a great circle) of the great circle line connecting the cell centers.

Usage

is_between(
  bf,
  points = NULL,
  radius = NULL,
  n_directions = 1,
  skip_unconnected = TRUE,
  batch_size = 1e+05,
  check_radius = TRUE
)

Arguments

bf

A BirdFlow model

points

The points to evaluate betweenness on. If NULL the cell centers of all the raster cells within the BirdFlow model that are between active cells in the model will be used. This is calculated by comparing the cell centers to a buffered convex hull around the active cell centers.

radius

A point is considered between two locations if it is within radius meters (along a great circle) of the great circle line between the locations. radius defaults to half the cell size (mean(res(bf))/2).

n_directions

The number of (equally spaced) directional bins to classify bearings into. Currently only 1 is supported.

skip_unconnected

If TRUE then only connections that exist in bf will be evaluated, and between matrix will erroneously indicate that no points are between locations that are not connected. The resulting array can still be used with the model it was built for because those missing connections would always have zero probability.

batch_size

controls the number of movement lines that are processed at a time. A smaller batch_size will conserve memory at a slight performance cost. The number of batches will be less than or equal to n_active(bf)^2 / batch_size.

check_radius

If TRUE an error will be thrown if the radius is not between the resolution and 1/4 the resolution of bf. Outside of that range the algorithm is likely to yield distorted results. 0.5 * mean(res(bf)) is the default, and recommended radius.

Value

A list with:

between

An array with dimensions representing the "from" location, the "to" location, and the points. Cells are TRUE if the point is between the associated from and to locations.

points

A data,frame of points that define the third dimension in between. It is identical to the input points if they are not NULL. Otherwise it will be a data frame with columns x, y, and i corresponding to the third dimension in between. i will be NA for points that are not within the mask but fall between active cells.

radius

The radius of the circle in meters.

Details

If points and radius are NULL they default to the cell radius and the center of all cells within the BirdFlow extent that fall between any active cells. This includes all cell centers within a convex hull (in spherical coordinates) around the active cells in bf.