R: Centroid of a window

centroid.owin {spatstat} | R Documentation

## Centroid of a window

### Description

Computes the centroid (centre of mass) of a window

### Usage

     centroid.owin(w, as.ppp = FALSE)

### Arguments

`w` | A window
`as.ppp` | Logical flag indicating whether to return the centroid as a point pattern (`ppp` object)

### Details

The centroid of the window `w` is computed. The centroid (“centre of mass”) is the point whose x and y coordinates are the mean values of the x and y coordinates of all points in the window.

The argument `w` should be a window (an object of class `"owin"`, see `owin.object` for details) or can be given in any format acceptable to `as.owin()`.

The calculation uses an exact analytic formula for the case of polygonal windows.

Note that the centroid of a window is not necessarily inside the window, unless the window is convex. If `as.ppp=TRUE` and the centroid of `w` lies outside `w`, then the window of the returned point pattern will be a rectangle containing the original window (using `as.rectangle`.

### Value

Either a list with components `x, y`, or a point pattern (of class `ppp`) consisting of a single point, giving the coordinates of the centroid of the window `w`.

### 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`

### Examples

      w <- owin(c(0,1),c(0,1))
      centroid.owin(w)
      # returns 0.5, 0.5

      data(demopat)
      w <- Window(demopat)
      # an irregular window
      cent <- centroid.owin(w, as.ppp = TRUE)
      ## Not run:
      plot(cent)
      # plot the window and its centroid

    ## End(Not run)

      wapprox <- as.mask(w)
      # pixel approximation of window
      ## Not run:
      points(centroid.owin(wapprox))
      # should be indistinguishable

    ## End(Not run)

[Package spatstat version 1.54-0 Index]