R: Superimpose Several Geometric Patterns

superimpose {spatstat.geom} | R Documentation

## Superimpose Several Geometric Patterns

### Description

Superimpose any number of point patterns or line segment patterns.

### Usage

      superimpose(...)

      ## S3 method for class 'ppp'
    superimpose(..., W=NULL, check=TRUE)

      ## S3 method for class 'psp'
    superimpose(..., W=NULL, check=TRUE)

      ## S3 method for class 'splitppp'
    superimpose(..., W=NULL, check=TRUE)

      ## S3 method for class 'ppplist'
    superimpose(..., W=NULL, check=TRUE)

      ## Default S3 method:
    superimpose(...)

### Arguments

`...` | Any number of arguments, each of which represents either a point pattern or a line segment pattern or a list of point patterns.
`W` | Optional. Data determining the window for the resulting pattern. Either a window (object of class `"owin"`, or something acceptable to `as.owin`), or a function which returns a window, or one of the strings `"convex"`, `"rectangle"`, `"bbox"` or `"none"`.
`check` | Logical value (passed to `ppp` or `psp` as appropriate) determining whether to check the geometrical validity of the resulting pattern.

### Details

This function is used to superimpose several geometric patterns of the same kind, producing a single pattern of the same kind.

The function `superimpose` is generic, with methods for the class `ppp` of point patterns, the class `psp` of line segment patterns, and a default method. There is also a method for `lpp`, described separately in `superimpose.lpp`.

The dispatch to a method is initially determined by the class of the first argument in `...`.

- `default`: If the first argument is not an object of class `ppp` or `psp`, then the default method `superimpose.default` is executed. This checks the class of all arguments, and dispatches to the appropriate method. Arguments of class `ppplist` can be handled.

- `ppp`: If the first `...` argument is an object of class `ppp` then the method `superimpose.ppp` is executed. All arguments in `...` must be either `ppp` objects or lists with components `x` and `y`. The result will be an object of class `ppp`.

- psp: If the first `...` argument is an object of class `psp` then the `psp` method is dispatched and all `...` arguments must be `psp` objects. The result is a `psp` object.

The patterns are not required to have the same window of observation.

The window for the superimposed pattern is controlled by the argument `W`.

- If `W` is a window (object of class `"W"` or something acceptable to `as.owin`) then this determines the window for the superimposed pattern.

- If `W` is `NULL`, or the character string `"none"`, then windows are extracted from the geometric patterns, as follows. For `superimpose.psp`, all arguments `...` are line segment patterns (objects of class `"psp"`); their observation windows are extracted; the union of these windows is computed; and this union is taken to be the window for the superimposed pattern. For `superimpose.ppp` and `superimpose.default`, the arguments `...` are inspected, and any arguments which are point patterns (objects of class `"ppp"`) are selected; their observation windows are extracted, and the union of these windows is taken to be the window for the superimposed point pattern. For `superimpose.default` if none of the arguments is of class `"ppp"` then no window is computed and the result of `superimpose` is a `list(x,y)`.

- If `W` is one of the strings `"convex"`, `"rectangle"` or `"bbox"` then a window for the superimposed pattern is computed from the coordinates of the points or the line segments as follows.

  `"bbox"`:

    the bounding box of the points or line segments (see `bounding.box.xy`);

  `"convex"`:

    the Ripley-Rasson estimator of a convex window (see `ripras`);

  `"rectangle"`:

    the Ripley-Rasson estimator of a rectangular window (using `ripras` with argument `shape="rectangle"`).

- If `W` is a function, then this function is used to compute a window for the superimposed pattern from the coordinates of the points or the line segments. The function should accept input of the form `list(x,y)` and is expected to return an object of class `"owin"`. Examples of such functions are `ripras` and `bounding.box.xy`.

The arguments `...` may be marked patterns. The marks of each component pattern must have the same format. Numeric and character marks may be “mixed”. If there is such mixing then the numeric marks are coerced to character in the combining process. If the mark structures are all data frames, then these data frames must have the same number of columns and identical column names.

If the arguments `...` are given in the form `name=value`, then the `name`s will be used as an extra column of marks attached to the elements of the corresponding patterns.

### Value

For `superimpose.ppp`, a point pattern (object of class `"ppp"`). For `superimpose.default`, either a point pattern (object of class `"ppp"`) or a `list(x,y)`. For `superimpose.psp`, a line segment pattern (object of class `"psp"`).

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au and Rolf Turner r.turner@auckland.ac.nz.

### See Also

`concatxy`, `quadscheme`.

### Examples

      # superimposing point patterns
      p1  <- runifrect(30)
      p2  <- runifrect(42)
      s1  <- superimpose(p1,p2) # Unmarked pattern.
      p3  <- list(x=rnorm(20),y=rnorm(20))
      s2  <- superimpose(p3,p2,p1) # Default method gets called.
      s2a <- superimpose(p1,p2,p3) # Same as s2 except for order of points.
      s3  <- superimpose(clyde=p1,irving=p2) # Marked pattern; marks a factor
                                             # with levels "clyde" and "irving";
                                             # warning given.
      marks(p1) <- factor(sample(LETTERS[1:3],30,TRUE))
      marks(p2) <- factor(sample(LETTERS[1:3],42,TRUE))
      s5  <- superimpose(clyde=p1,irving=p2) # Marked pattern with extra column
      marks(p2) <- data.frame(a=marks(p2),b=runif(42))
      s6  <- try(superimpose(p1,p2)) # Gives an error.
      marks(p1) <- data.frame(a=marks(p1),b=1:30)
      s7  <- superimpose(p1,p2) # O.K.

      # how to make a 2-type point pattern with types "a" and "b"
      u <- superimpose(a = runifrect(10), b = runifrect(20))

      # how to make a 2-type point pattern with types 1 and 2
      u <- superimpose("1" = runifrect(10), "2" = runifrect(20))

      # superimposing line segment patterns
      X <- as.psp(matrix(runif(20), 5, 4), window=owin())
      Y <- as.psp(matrix(runif(40), 10, 4), window=owin())
      Z <- superimpose(X, Y)

      # being unreasonable
      ## Not run:
       if(FALSE) {
        crud <- try(superimpose(p1,p2,X,Y)) # Gives an error, of course!
       }

    ## End(Not run)

[Package spatstat.geom version 2.3-2 Index]