polygrid {geoR} | R Documentation |
Coordinates of Points Inside a Polygon
Description
This function builds a rectangular grid and extracts points which are inside of an internal polygonal region.
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 |
... |
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:
xypoly |
an |
vec.inout |
logical, a vector indicating whether each point of
the rectangular grid is inside the polygon. Only returned if |
Author(s)
Paulo Justiniano Ribeiro Jr. paulojus@leg.ufpr.br,
Peter J. Diggle p.diggle@lancaster.ac.uk.
References
Further information on the package geoR can be found at:
http://www.leg.ufpr.br/geoR/.
See Also
pred_grid
, expand.grid
, over
,
SpatialPoints
.
Examples
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)