R: Mark of Nearest Neighbour

nnmark {spatstat} | R Documentation

## Mark of Nearest Neighbour

### Description

Given a marked point pattern dataset `X` this function computes, for each desired location `y`, the mark attached to the nearest neighbour of `y` in `X`. The desired locations `y` can be either a pixel grid or the point pattern `X` itself.

### Usage

    nnmark(X, ..., k = 1, at=c("pixels", "points"))

### Arguments

`X` | A marked point pattern (object of class `"ppp"`).
`...` | Arguments passed to `as.mask` to determine the pixel resolution.
`k` | Single integer. The `k`th nearest data point will be used.
`at` | String specifying whether to compute the values at a grid of pixel locations (`at="pixels"`) or only at the points of `X` (`at="points"`).

### Details

Given a marked point pattern dataset `X` this function computes, for each desired location `y`, the mark attached to the point of `X` that is nearest to `y`. The desired locations `y` can be either a pixel grid or the point pattern `X` itself.

The argument `X` must be a marked point pattern (object of class `"ppp"`, see `ppp.object`). The marks are allowed to be a vector or a data frame.

- If `at="points"`, then for each point in `X`, the algorithm finds the nearest other point in `X`, and extracts the mark attached to it. The result is a vector or data frame containing the marks of the neighbours of each point.

- If `at="pixels"` (the default), then for each pixel in a rectangular grid, the algorithm finds the nearest point in `X`, and extracts the mark attached to it. The result is an image or a list of images containing the marks of the neighbours of each pixel. The pixel resolution is controlled by the arguments `...` passed to `as.mask`.

If the argument `k` is given, then the `k`-th nearest neighbour will be used.

### Value

If `X` has a single column of marks:

- If `at="pixels"` (the default), the result is a pixel image (object of class `"im"`). The value at each pixel is the mark attached to the nearest point of `X`.

- If `at="points"`, the result is a vector or factor of length equal to the number of points in `X`. Entries are the mark values of the nearest neighbours of each point of `X`.

If `X` has a data frame of marks:

- If `at="pixels"` (the default), the result is a named list of pixel images (object of class `"im"`). There is one image for each column of marks. This list also belongs to the class `"solist"`, for which there is a plot method.

- If `at="points"`, the result is a data frame with one row for each point of `X`, Entries are the mark values of the nearest neighbours of each point of `X`.

### 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

`Smooth.ppp`, `marktable`, `nnwhich`

### Examples

      plot(nnmark(ants))
      v <- nnmark(ants, at="points")
      v[1:10]
      plot(nnmark(finpines))
      vf <- nnmark(finpines, at="points")
      vf[1:5,]

[Package spatstat version 1.63-3 Index]