R: Rotational Average of a Pixel Image

rotmean {spatstat} | 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"))

### 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.

### Details

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

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 r is the average value of the image `X` over the entire circle of radius r, 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 r that lies entirely inside the window.

### Value

An object of class `"fv"` or `"im"`.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

Rolf Turner r.turner@auckland.ac.nz

and Ege Rubak rubak@math.aau.dk

### Examples

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

[Package spatstat version 1.63-3 Index]