View source: R/sample_background.R
sample_background | R Documentation |
This function samples background points from a raster given a set of presences. The locations returned as the center points of the sampled cells, which can overlap with the presences (in contrast to pseudo-absences, see sample_pseudoabs). The following methods are implemented:
'random': background randomly sampled from the region covered by the raster (i.e. not NAs).
'dist_max': background randomly sampled from the unioned buffers of 'dist_max' from presences (distances in 'm' for lonlat rasters, and in map units for projected rasters). Using the union of buffers means that areas that are in multiple buffers are not oversampled. This is also referred to as "thickening".
'bias': background points are sampled according to a surface representing the biased sampling effort.
sample_background(
data,
raster,
n,
coords = NULL,
method = "random",
class_label = "background",
return_pres = TRUE
)
data |
An |
raster |
the terra::SpatRaster or |
n |
number of background points to sample. |
coords |
a vector of length two giving the names of the "x" and "y"
coordinates, as found in |
method |
sampling method. One of 'random', 'dist_max', and 'bias'. For dist_max, the maximum distance is set as an additional element of a vector, e.g c('dist_max',70000). |
class_label |
the label given to the sampled points. Defaults to
|
return_pres |
return presences together with background in a single tibble. |
Note that the units of distance depend on the projection of the raster.
An object of class tibble::tibble. If presences are returned, the
presence level is set as the reference (to match the expectations in the
yardstick
package that considers the first level to be the event).
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