polygrid {geoR} | R Documentation |
This function builds a rectangular grid and extracts points which are inside of an internal polygonal region.
polygrid(xgrid, ygrid, borders, vec.inout = FALSE)
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 TRUE a logical vector is included
in the output indicating whether each point of the grid is inside
the polygon. Defaults to FALSE . |
This function requires the package splancs
.
The function works as follows:
First it creates a grid using the R function
expand.grid
and then it uses the function
inout
from the package splancs
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.
A list with components:
xypoly |
an n x 2 matrix with the coordinates of the points inside the polygon. |
vec.inout |
logical, a vector indicating whether each point of
the rectangular grid is inside the polygon. Only returned if vec.inout = TRUE . |
Paulo Justiniano Ribeiro Jr. Paulo.Ribeiro@est.ufpr.br,
Peter J. Diggle p.diggle@lancaster.ac.uk.
Further information on the package geoR can be found at:
http://www.est.ufpr.br/geoR.
if(require(splancs)){ 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) }