R: Class of Point Patterns

ppp.object {spatstat.geom} | R Documentation

## Class of Point Patterns

### Description

A class `"ppp"` to represent a two-dimensional point pattern. Includes information about the window in which the pattern was observed. Optionally includes marks.

### Details

This class represents a two-dimensional point pattern dataset. It specifies

- the locations of the points

- the window in which the pattern was observed

- optionally, “marks” attached to each point (extra information such as a type label).

If `X` is an object of type `ppp`, it contains the following elements:

`x` | vector of x coordinates of data points
`y` | vector of y coordinates of data points
`n` | number of points
`window` | window of observation
| (an object of class `owin`)
`marks` | optional vector or data frame of marks

Users are strongly advised not to manipulate these entries directly.

Objects of class `"ppp"` may be created by the function `ppp` and converted from other types of data by the function `as.ppp`. Note that you must always specify the window of observation; there is intentionally no default action of “guessing” the window dimensions from the data points alone.

Standard point pattern datasets provided with the package include `amacrine`, `betacells`, `bramblecanes`, `cells`, `demopat`, `ganglia`, `lansing`, `longleaf`, `nztrees`, `redwood`, `simdat` and `swedishpines`.

Point patterns may be scanned from your own data files by `scanpp` or by using `read.table` and `as.ppp`.

They may be manipulated by the functions `[.ppp` and `superimpose`.

Point pattern objects can be plotted just by typing `plot(X)` which invokes the `plot` method for point pattern objects, `plot.ppp`. See `plot.ppp` for further information.

There are also methods for `summary` and `print` for point patterns. Use `summary(X)` to see a useful description of the data.

Patterns may be generated at random by `runifpoint`, `rpoispp`, `rMaternI`, `rMaternII`, `rSSI`, `rNeymanScott`, `rMatClust`, and `rThomas`.

Most functions which are intended to operate on a window (of class `owin`) will, if presented with a `ppp` object instead, automatically extract the window information from the point pattern.

### Warnings

The internal representation of marks is likely to change in the next release of this package.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

and Rolf Turner r.turner@auckland.ac.nz

### See Also

`owin`, `ppp`, `as.ppp`, `[.ppp`

### Examples

      x <- runif(100)
      y <- runif(100)
      X <- ppp(x, y, c(0,1),c(0,1))
      X
      if(human <- interactive()) plot(X)
      mar <- sample(1:3, 100, replace=TRUE)
      mm <- ppp(x, y, c(0,1), c(0,1), marks=mar)
      if(human) plot(mm)
      # points with mark equal to 2
      ss <- mm[ mm$marks == 2 , ]
      if(human) plot(ss)
      # left half of pattern 'mm'
      lu <- owin(c(0,0.5),c(0,1))
      mmleft <- mm[ , lu]
      if(human) plot(mmleft)
      if(FALSE) {
      # input data from file
      qq <- scanpp("my.table", unit.square())
      # interactively build a point pattern
      plot(unit.square())
      X <- as.ppp(locator(10), unit.square())
      plot(X)
      }

[Package spatstat.geom version 2.2-0 Index]