R: Buffer Distance Tessellation

bufftess {spatstat.geom} | R Documentation

## Buffer Distance Tessellation

### Description

Constructs a spatial tessellation, composed of rings or buffers at specified distances away from the given spatial object.

### Usage

    bufftess(X, breaks, W = Window(X), ..., polygonal = TRUE)

### Arguments

`X` | A spatial object in two dimensions, such as a point pattern (class `"ppp"`) or line segment pattern (class `"psp"`).
`breaks` | Either a numeric vector specifying the cut points for the distance values, or a single integer specifying the number of cut points.
`W` | Optional. Window (object of class `"owin"`) inside which the tessellation will be constructed.
`...` | Optional arguments passed to `as.mask` controlling the pixel resolution when `polygonal=FALSE`, and optional arguments passed to `cut.default` controlling the labelling of the distance bands.
`polygonal` | Logical value specifying whether the tessellation should consist of polygonal tiles (`polygonal=TRUE`, the default) or should be constructed using a pixel image (`polygonal=FALSE`).

### Details

This function divides space into tiles defined by distance from the object `X`. The result is a tessellation (object of class `"tess"`) that consists of concentric rings around `X`.

The distance values which determine the tiles are specified by the argument `breaks`.

- If `breaks` is a vector of numerical values, then these values are taken to be the distances defining the tiles. The first tile is the region of space that lies at distances between `breaks[1]` and `breaks[2]` away from `X`; the second tile is the region lying at distances between `breaks[2]` and `breaks[3]` away from `X`; and so on. The number of tiles will be `length(breaks)-1`.

- If `breaks` is a single integer, it is interpreted as specifying the number of intervals between breakpoints. There will be `breaks+1` equally spaced break points, ranging from zero to the maximum achievable distance. The number of tiles will equal `breaks`.

The tessellation can be computed using either raster calculations or vector calculations.

- If `polygonal=TRUE` (the default), the tiles are computed as polygonal windows using vector geometry, and the result is a tessellation consisting of polygonal tiles. This calculation could be slow and could require substantial memory, but produces a geometrically accurate result.

- If `polygonal=FALSE`, the distance map of `X` is computed as a pixel image (`distmap`), then the distance values are divided into discrete bands using `cut.im`. The result is a tessellation specified by a pixel image. This computation is faster but less accurate.

### Value

A tessellation (object of class `"tess"`).

### 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

Polygonal calculations are performed using `dilation` and `setminus.owin`. Pixel calculations are performed using `distmap` and `cut.im`. See `as.mask` for details of arguments that control pixel resolution.

For other kinds of tessellations, see `tess`, `hextess`, `venn.tess`, `polartess`, `dirichlet`, `delaunay`, `quantess`, `quadrats` and `rpoislinetess`.

### Examples

      X <- cells[c(FALSE,FALSE,FALSE,TRUE)]
      b <- c(0, 0.05, 0.1, 0.15, 0.2, Inf)
      plot(bufftess(X, b), do.col=TRUE, col=1:5)

[Package spatstat.geom version 2.3-2 Index]