R: Extract Subset of Multidimensional Point Pattern

Extract.ppx {spatstat.geom} | R Documentation

## Extract Subset of Multidimensional Point Pattern

### Description

Extract a subset of a multidimensional point pattern.

### Usage

      ## S3 method for class 'ppx'
    x[i, drop=FALSE, clip=FALSE, ...]

### Arguments

`x` | A multidimensional point pattern (object of class `"ppx"`).
`i` | Subset index. A valid subset index in the usual R sense, indicating which points should be retained; or a spatial domain of class `"boxx"` or `"box3"`.
`drop` | Logical value indicating whether to remove unused levels of the marks, if the marks are a factor.
`clip` | Logical value indicating how to form the domain of the resulting point pattern, when `i` is a box (object of class `"boxx"`). If `clip=FALSE` (the default), the result has domain equal to `i`. If `clip=TRUE`, the resulting domain is the intersection between the domain of `x` and the domain `i`.
`...` | Ignored.

### Details

This function extracts a designated subset of a multidimensional point pattern.

The function `[.ppx` is a method for `[` for the class `"ppx"`. It extracts a designated subset of a point pattern. The argument `i` may be either

- a subset index in the usual R sense: either a numeric vector of positive indices (identifying the points to be retained), a numeric vector of negative indices (identifying the points to be deleted) or a logical vector of length equal to the number of points in the point pattern `x`. In the latter case, the points `(x$x[i], x$y[i])` for which `subset[i]=TRUE` will be retained, and the others will be deleted.

- a spatial domain of class `"boxx"` or `"box3"`. Points falling inside this region will be retained.

The argument `drop` determines whether to remove unused levels of a factor, if the point pattern is multitype (i.e. the marks are a factor) or if the marks are a data frame or hyperframe in which some of the columns are factors.

Use the function `unmark` to remove marks from a marked point pattern.

### Value

A multidimensional point pattern (of class `"ppx"`).

### 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

`ppx`

### Examples

       df <- data.frame(x=runif(4),y=runif(4),z=runif(4))
       X <- ppx(data=df, coord.type=c("s","s","t"))
       X[-2]
       Y <- ppx(coords(cells), domain = boxx(c(0,1),c(0,1)))
       dom <- shift(domain(Y), vec = c(.5,.5))
       Y[dom]
       Y[dom, clip=TRUE]

[Package spatstat.geom version 2.3-2 Index]