as.polygonal

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Convert a Window to a Polygonal Window

Given a window W of any geometric type (rectangular, polygonal or binary mask), this function returns a polygonal window that represents the same spatial domain.

Keywords
manip, spatial
Usage
as.polygonal(W, repair=FALSE)
Arguments
W

A window (object of class "owin").

repair

Logical value indicating whether to check the validity of the polygon data and repair it, if W is already a polygonal window.

Details

Given a window W of any geometric type (rectangular, polygonal or binary mask), this function returns a polygonal window that represents the same spatial domain.

If W is a rectangle, it is converted to a polygon with 4 vertices.

If W is already polygonal, it is returned unchanged, by default. However if repair=TRUE then the validity of the polygonal coordinates will be checked (for example to check the boundary is not self-intersecting) and repaired if necessary, so that the result could be different from W.

If W is a binary mask, then each pixel in the mask is replaced by a small square or rectangle, and the union of these squares or rectangles is computed. The result is a polygonal window that has only horizontal and vertical edges. (Use simplify.owin to remove the staircase appearance, if desired).

Value

A polygonal window (object of class "owin" and of type "polygonal").

See Also

owin, as.owin, as.mask, simplify.owin

• as.polygonal
Examples
# NOT RUN {
data(letterR)
m <- as.mask(letterR, dimyx=32)
p <- as.polygonal(m)
if(interactive()) {
plot(m)
plot(p, add=TRUE, lwd=2)
}
# }

Documentation reproduced from package spatstat, version 1.61-0, License: GPL (>= 2)

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