polygrid
Coordinates of Points Inside a Polygon
This function builds a rectangular grid and extracts points which are inside of an internal polygonal region.
- Keywords
- spatial
Usage
polygrid(xgrid, ygrid, borders, vec.inout = FALSE, ...)Arguments
- xgrid
grid values in the x-direction.
- ygrid
grid values in the y-direction.
- borders
a matrix with polygon coordinates defining the borders of the region.
- vec.inout
logical. If
TRUEa logical vector is included in the output indicating whether each point of the grid is inside the polygon. Defaults toFALSE.- ...
currently not used (kept for back compatibility).
Details
The function works as follows:
First it creates a grid using the R function
expand.grid and then it uses the geoR'
internal function
.geoR_inout() which wraps usage of SpatialPoints
and over
from the package sp to extract the points
of the grid which are inside the polygon.
Within the package geoR
this function is typically used to select points in a non-rectangular
region to perform spatial prediction
using krige.bayes, krige.conv or
ksline. It is also useful to produce
image or perspective plots of the prediction results.
Value
A list with components:
an \(n \times 2\) matrix with the coordinates of the points inside the polygon.
logical, a vector indicating whether each point of
the rectangular grid is inside the polygon. Only returned if vec.inout = TRUE.
References
Further information on the package geoR can be found at: http://www.leg.ufpr.br/geoR.
See Also
Examples
# NOT RUN {
poly <- matrix(c(.2, .8, .7, .1, .2, .1, .2, .7, .7, .1), ncol=2)
plot(0:1, 0:1, type="n")
lines(poly)
poly.in <- polygrid(seq(0,1,l=11), seq(0,1,l=11), poly, vec=TRUE)
points(poly.in$xy)
# }