| ecospat.rand.pseudoabsences {ecospat} | R Documentation |
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 olivier.broennimann@unil.ch
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)