# in.out

From mgcv v1.8-16
by Simon Wood

##### Which of a set of points lie within a polygon defined region

Tests whether each of a set of points lie within a region defined by one or more (possibly nested) polygons. Points count as `inside' if they are interior to an odd number of polygons.

##### Usage

`in.out(bnd,x)`

##### Arguments

- bnd
- A two column matrix, the rows of which define the vertices of polygons defining the boundary of a region.
Different polygons should be separated by an
`NA`

row, and the polygons are assumed closed. - x
- A two column matrix. Each row is a point to test for inclusion in the region defined by
`bnd`

.

##### Details

The algorithm works by counting boundary crossings (using compiled C code).

##### Value

`nrow(x)`

. `TRUE`

if the corresponding row of `x`

is inside
the boundary and `FALSE`

otherwise.
##### References

##### Examples

`library(mgcv)`

```
library(mgcv)
data(columb.polys)
bnd <- columb.polys[[2]]
plot(bnd,type="n")
polygon(bnd)
x <- seq(7.9,8.7,length=20)
y <- seq(13.7,14.3,length=20)
gr <- as.matrix(expand.grid(x,y))
inside <- in.out(bnd,gr)
points(gr,col=as.numeric(inside)+1)
```

*Documentation reproduced from package mgcv, version 1.8-16, License: GPL (>= 2)*

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