nnmark

0th

Percentile

Mark of Nearest Neighbour

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.

Keywords
methods, smooth, spatial
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 kth 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.

See Also

Smooth.ppp, marktable, nnwhich

Aliases
  • nnmark
Examples
# NOT RUN {
  plot(nnmark(ants))
  v <- nnmark(ants, at="points")
  v[1:10]
  plot(nnmark(finpines))
  vf <- nnmark(finpines, at="points")
  vf[1:5,]
# }
Documentation reproduced from package spatstat, version 1.59-0, License: GPL (>= 2)

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