R: Convert a Window to a Polygonal Window

as.polygonal {spatstat} | R Documentation

## 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.

### 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"`).

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk

### See Also

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

### Examples

       data(letterR)
       m <- as.mask(letterR, dimyx=32)
       p <- as.polygonal(m)
       if(interactive()) {
          plot(m)
          plot(p, add=TRUE, lwd=2)
       }

[Package spatstat version 1.63-3 Index]