intersect.owin: Intersection, Union or Set Subtraction of Windows

Description

Yields the intersection, union or set subtraction of windows.

Usage

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

Arguments

A,B

Windows (objects of class "owin") or data acceptable to as.owin.

...

Windows, or arguments passed to as.mask to control the discretisation.

fatal

Logical. Determines what happens if the intersection is empty.

Optional list of parameters passed to polyclip to control the accuracy of polygon geometry.

Value

A window (object of class "owin") or possibly NULL.

Details

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

For intersect.owin and union.owin, the arguments ... must be either

window objects of class"owin",
data that can be coerced to this class byas.owin),
lists of windows, of class"solist",
named arguments ofas.maskto control the discretisation if required.

For setminus.owin, the arguments ... must be named arguments of as.mask.

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

Examples

Run this code

# 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))

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