Intersection, Union or Set Subtraction of Two Windows

Description

Yields the intersection, union or set subtraction of two windows.

Usage

   intersect.owin(A, B, ..., fatal=TRUE)
   union.owin(A,B, ...)
   setminus.owin(A,B, ...)

Arguments

Details

The function intersect.owin computes the intersection between the two windows A and B, while union.owin computes their union. The function setminus.owin computes the intersection of A with the complement of B.

The arguments A and B must be window objects (either objects of class "owin", or data that can be coerced to this class by as.owin).

If the intersection is empty, then if fatal=FALSE the result is NULL, while if fatal=TRUE an error occurs.

The intersection or union of more than two windows can also be computed. For intersect.owin and union.owin the arguments ... can include additional window objects.

Value

A window (object of class "owin").

Author(s)

Adrian Baddeley Adrian.Baddeley@uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner r.turner@auckland.ac.nz

See Also

is.subset.owin, overlap.owin, boundingbox, owin.object

Examples

# rectangles
   u <- unit.square()
   v <- owin(c(0.5,3.5), c(0.4,2.5))
# polygon
   data(letterR)
# mask
   m <- as.mask(letterR)

# two rectangles
   intersect.owin(u, v) 
   union.owin(u,v)
   setminus.owin(u,v)

# polygon and rectangle
   intersect.owin(letterR, v)
   union.owin(letterR,v)
   setminus.owin(letterR,v)

# mask and rectangle
   intersect.owin(m, v)
   union.owin(m,v)
   setminus.owin(m,v)

# mask and polygon
   p <- rotate(v, 0.2)
   intersect.owin(m, p)
   union.owin(m,p)
   setminus.owin(m,p)

# two polygons
   A <- letterR
   B <- rotate(letterR, 0.2)
   plot(boundingbox(A,B), main="intersection")
   w <- intersect.owin(A, B)
   plot(w, add=TRUE, col="lightblue")
   plot(A, add=TRUE)
   plot(B, add=TRUE)

   plot(boundingbox(A,B), main="union")
   w <- union.owin(A,B)
   plot(w, add=TRUE, col="lightblue")   
   plot(A, add=TRUE)
   plot(B, add=TRUE)

   plot(boundingbox(A,B), main="set minus")
   w <- setminus.owin(A,B)
   plot(w, add=TRUE, col="lightblue")   
   plot(A, add=TRUE)
   plot(B, add=TRUE)

# intersection and union of three windows
   C <- shift(B, c(0.2, 0.3))
   plot(union.owin(A,B,C))
   plot(intersect.owin(A,B,C))