Convex Hull

0th

Percentile

Convex hull model

The Convex Hull model predicts that a species is present at sites inside the convex hull of a set of training points, and absent outside that hull. I.e. this is the spatial convex hull, not an environmental hull.

Keywords
spatial
Usage
convHull(p, ...)
Arguments
p
point locations (presence). Two column matrix, data.frame or SpatialPoints* object
...
Additional arguments. See details
Details

You can supply an argument n (>= 1) to get n convex hulls around subset of the points. You can also set n=1:x, to get a set of overlapping polygons consisting of 1 to x parts. I.e. the first polygon has 1 part, the second has 2 parts, and x has x parts.

Value

  • An object of class 'ConvexHull'

See Also

predict, geoDist, maxent, domain, mahal

Aliases
  • convHull
  • convHull,SpatialPoints-method
  • convHull,matrix-method
  • convHull,data.frame-method
Examples
r <- raster(system.file("external/rlogo.grd", package="raster"))
#presence data
pts <- matrix(c(17, 42, 85, 70, 19, 53, 26, 84, 84, 46, 48, 85, 4, 95, 48, 54, 66, 74, 50, 48, 28, 73, 38, 56, 43, 29, 63, 22, 46, 45, 7, 60, 46, 34, 14, 51, 70, 31, 39, 26), ncol=2)
train <- pts[1:12, ]
test <- pts[13:20, ]
				 
ch <- convHull(train)
predict(ch, test)

plot(r)
plot(ch@hull, border='red', lwd=2, add=TRUE)
points(train, col='red', pch=20, cex=2)
points(test, col='black', pch=20, cex=2)

pr = predict(ch, r, progress='')
plot(r, legend=FALSE)
plot(pr, add=TRUE, col='blue')
points(test, col='black', pch=20, cex=2)
points(train, col='red', pch=20, cex=2)
Documentation reproduced from package dismo, version 0.5-1, License: GPL (>= 3)

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