R: Evaluate Expression Involving Function Arrays

eval.fasp {spatstat} | R Documentation

## Evaluate Expression Involving Function Arrays

### Description

Evaluates any expression involving one or more function arrays (`fasp` objects) and returns another function array.

### Usage

      eval.fasp(expr, envir, dotonly=TRUE)

### Arguments

`expr` | An expression involving the names of objects of class `"fasp"`.
`envir` | Optional. The environment in which to evaluate the expression, or a named list containing `"fasp"` objects to be used in the expression.
`dotonly` | Logical. Passed to `eval.fv`.

### Details

This is a wrapper to make it easier to perform pointwise calculations with the arrays of summary functions used in spatial statistics.

A function array (object of class `"fasp"`) can be regarded as a matrix whose entries are functions. Objects of this kind are returned by the command `alltypes`.

Suppose `X` is an object of class `"fasp"`. Then `eval.fasp(X+3)` effectively adds 3 to the value of every function in the array `X`, and returns the resulting object.

Suppose `X` and `Y` are two objects of class `"fasp"` which are compatible (for example the arrays must have the same dimensions). Then `eval.fasp(X + Y)` will add the corresponding functions in each cell of the arrays `X` and `Y`, and return the resulting array of functions.

Suppose `X` is an object of class `"fasp"` and `f` is an object of class `"fv"`. Then `eval.fasp(X + f)` will add the function `f` to the functions in each cell of the array `X`, and return the resulting array of functions.

In general, `expr` can be any expression involving (a) the names of objects of class `"fasp"` or `"fv"`, (b) scalar constants, and (c) functions which are vectorised. See the Examples.

First `eval.fasp` determines which of the variable names in the expression `expr` refer to objects of class `"fasp"`. The expression is then evaluated for each cell of the array using `eval.fv`.

The expression `expr` must be vectorised. There must be at least one object of class `"fasp"` in the expression. All such objects must be compatible.

### Value

Another object of class `"fasp"`.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

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

### See Also

`fasp.object`, `Kest`

### Examples

      # manipulating the K function
      K <- alltypes(amacrine, "K")

      # expressions involving a fasp object
      eval.fasp(K + 3)
      L <- eval.fasp(sqrt(K/pi))

      # expression involving two fasp objects
      D <- eval.fasp(K - L)

      # subtracting the unmarked K function from the cross-type K functions
      K0 <- Kest(unmark(amacrine))
      DK <- eval.fasp(K - K0)

      ## Use of 'envir'
      S <- eval.fasp(1-G, list(G=alltypes(amacrine, "G")))

[Package spatstat version 1.63-3 Index]