ecospat.rand.pseudoabsences: Sample Pseudo-Absences

In ecospat: Spatial Ecology Miscellaneous Methods

Sample Pseudo-Absences

Description

Randomly sample pseudoabsences from an environmental dataframe covering the study area.

Usage

ecospat.rand.pseudoabsences (nbabsences, glob, colxyglob, colvar="all", 
presence, colxypresence, mindist)

Arguments

nbabsences	The number of pseudoabsences desired.
glob	A two-column dataframe (or a vector) of the environmental values (in column) for background pixels of the whole study area (in row).
colxyglob	The range of columns for x and y in glob.
colvar	The range of columns for the environmental variables in glob. colvar="all" keeps all the variables in glob in the final dataframe. colvar=NULL keeps only x and y.
presence	A presence-absence dataframe for each species (columns) in each location or grid cell (rows).
colxypresence	The range of columns for x and y in presence.
mindist	The minimum distance from presences within wich pseudoabsences should not be drawn (buffer distance around presences).

Value

A dataframe of random absences.

Author(s)

Olivier Broennimann [e-mail]

Examples

glob <- ecospat.testData[2:8]
presence <- ecospat.testData[c(2:3,9)]
presence <- presence[presence[,3]==1,1:2]
ecospat.rand.pseudoabsences (nbabsences=10, glob=glob, colxyglob=1:2, colvar = "all", 
presence= presence, colxypresence=1:2, mindist=20)

ecospat documentation built on July 4, 2024, 5:06 p.m.