rotmean {spatstat.explore}R Documentation

Rotational Average of a Pixel Image

Description

Compute the average pixel value over all rotations of the image about the origin, as a function of distance from the origin.

Usage

rotmean(X, ..., origin, padzero=TRUE, Xname, result=c("fv", "im"), adjust=1)

Arguments

X

A pixel image.

...

Ignored.

origin

Optional. Origin about which the rotations should be performed. Either a numeric vector or a character string as described in the help for shift.owin.

padzero

Logical. If TRUE (the default), the value of X is assumed to be zero outside the window of X. If FALSE, the value of X is taken to be undefined outside the window of X.

Xname

Optional name for X to be used in the function labels.

result

Character string specifying the kind of result required: either a function object or a pixel image.

adjust

Adjustment factor for bandwidth used in kernel smoothing.

Details

This command computes, for each possible distance rr, the average pixel value of the pixels lying at distance rr from the origin. Kernel smoothing is used to obtain a smooth function of rr.

If result="fv" (the default) the result is a function object of class "fv" giving the mean pixel value of X as a function of distance from the origin.

If result="im" the result is a pixel image, with the same dimensions as X, giving the mean value of X over all pixels lying at the same distance from the origin as the current pixel.

If padzero=TRUE (the default), the value of X is assumed to be zero outside the window of X. The rotational mean at a given distance rr is the average value of the image X over the entire circle of radius rr, including zero values outside the window if the circle lies partly outside the window.

If padzero=FALSE, the value of X is taken to be undefined outside the window of X. The rotational mean is the average of the X values over the subset of the circle of radius rr that lies entirely inside the window.

Value

An object of class "fv" or "im", with the same coordinate units as X.

Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner rolfturner@posteo.net and Ege Rubak rubak@math.aau.dk.

See Also

radcumint

Examples

  online <- interactive()
  resolution <- if(online) 128 else 32
  Z <- setcov(square(1), dimyx=resolution)
  f <- rotmean(Z)
  if(online) {
    plot(rotmean(Z))
    plot(rotmean(Z, result="im"))
  }

[Package spatstat.explore version 3.3-1 Index]