spatstat (version 1.55-0)

as.polygonal: Convert a Window to a Polygonal Window

Description

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.

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.

Value

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

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).

See Also

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

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)
   }
# }