# on.convex.hull: Determines if points are on or in the convex hull of a... In interp: Interpolation Methods

## Description

Given a triangulation object `tri.obj` of n points in the plane, this subroutine returns a logical vector indicating if the points (x_i,y_i) lay on or in the convex hull of `tri.obj`.

## Usage

 ```1 2``` ```on.convex.hull(tri.obj, x, y, eps=1E-16) in.convex.hull(tri.obj, x, y, eps=1E-16, strict=TRUE) ```

## Arguments

 `tri.obj` object of class `triSht` `x` vector of x-coordinates of points to locate `y` vector of y-coordinates of points to locate `eps` accuracy for checking the condition `strict` logical, default `TRUE`. It indicates if the convex hull is treated as an open (`strict=TRUE`) or closed (`strict=FALSE`) set. (applies only to `in.convex.hull`)

Logical vector.

## Author(s)

Albrecht Gebhardt <albrecht.gebhardt@aau.at>, Roger Bivand <roger.bivand@nhh.no>

`triSht`, `print.triSht`, `plot.triSht`, `summary.triSht`, `triangles`, `convex.hull`.
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14``` ```# use a part of the quakes data set: data(quakes) quakes.part<-quakes[(quakes[,1]<=-10.78 & quakes[,1]>=-19.4 & quakes[,2]<=182.29 & quakes[,2]>=165.77),] q.tri<-tri.mesh(quakes.part\$lon, quakes.part\$lat, duplicate="remove") on.convex.hull(q.tri,quakes.part\$lon[1:20],quakes.part\$lat[1:20]) # Check with part of data set: # Note that points on the hull (see above) get marked FALSE below: in.convex.hull(q.tri,quakes.part\$lon[1:20],quakes.part\$lat[1:20]) # If points both on the hull and in the interior of the hull are meant # disable strict mode: in.convex.hull(q.tri,quakes.part\$lon[1:20],quakes.part\$lat[1:20],strict=FALSE) # something completely outside: in.convex.hull(q.tri,c(170,180),c(-20,-10)) ```