View source: R/sample_pseudoabs_time.R
sample_pseudoabs_time | R Documentation |
This function samples pseudo-absence points from a raster given a set of presences. The locations returned as the center points of the sampled cells, which can not overlap with the presences (in contrast to background points, see sample_background_time). The following methods are implemented:
'random': pseudo-absences randomly sampled from the region covered by the raster (i.e. not NAs).
'dist_min': pseudo-absences randomly sampled from the region excluding a buffer of 'dist_min' from presences (distances in 'm' for lonlat rasters, and in map units for projected rasters).
'dist_max': pseudo-absences 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".
'dist_disc': pseudo-absences randomly sampled from the unioned discs around presences with the two values of 'dist_disc' defining the minimum and maximum distance from presences.
sample_pseudoabs_time(
data,
raster,
n_per_presence,
coords = NULL,
time_col = "time",
lubridate_fun = c,
method = "random",
class_label = "pseudoabs",
return_pres = TRUE,
time_buffer = 0
)
data |
An |
raster |
the terra::SpatRaster, |
n_per_presence |
number of pseudoabsence points to sample for each presence |
coords |
a vector of length two giving the names of the "x" and "y"
coordinates, as found in |
time_col |
The name of the column with time; if time is not a lubridate
object, use |
lubridate_fun |
function to convert the time column into a lubridate object |
method |
sampling method. One of 'random', 'dist_min', 'dist_max', or 'dist_disc'. |
class_label |
the label given to the sampled points. Defaults to
|
return_pres |
return presences together with pseudoabsences in a single tibble |
time_buffer |
the buffer on the time axis around presences that defines
their effect when sampling pseudoabsences. If set to zero, presences have
an effect only on the time step to which they are assigned in |
#' @details Note that the time axis of the raster should be in POSIXct
or
Date
format, or use ‘tstep="years"’. See terra::time()
for details on how
to set the time axis.
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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