R: Calculate Derivative of Function Values

deriv.fv {spatstat.core} | R Documentation

## Calculate Derivative of Function Values

### Description

Applies numerical differentiation to the values in selected columns of a function value table.

### Usage

    ## S3 method for class 'fv'
    deriv(expr, which = "*", ...,
              method=c("spline", "numeric"),
              kinks=NULL,
              periodic=FALSE,
              Dperiodic=periodic)

### Arguments

`expr` | Function values to be differentiated. A function value table (object of class `"fv"`, see `fv.object`).
`which` | Character vector identifying which columns of the table should be differentiated. Either a vector containing names of columns, or one of the wildcard strings `"*"` or `"."` explained below.
`...` | Extra arguments passed to `smooth.spline` to control the differentiation algorithm, if `method="spline"`.
`method` | Differentiation method. A character string, partially matched to either `"spline"` or `"numeric"`.
`kinks` | Optional vector of x values where the derivative is allowed to be discontinuous.
`periodic` | Logical value indicating whether the function `expr` is periodic.
`Dperiodic` | Logical value indicating whether the resulting derivative should be a periodic function.

### Details

This command performs numerical differentiation on the function values in a function value table (object of class `"fv"`). The differentiation is performed either by `smooth.spline` or by a naive numerical difference algorithm.

The command `deriv` is generic. This is the method for objects of class `"fv"`.

Differentiation is applied to every column (or to each of the selected columns) of function values in turn, using the function argument as the x coordinate and the selected column as the y coordinate. The original function values are then replaced by the corresponding derivatives.

The optional argument `which` specifies which of the columns of function values in `expr` will be differentiated. The default (indicated by the wildcard `which="*"`) is to differentiate all function values, i.e.\ all columns except the function argument. Alternatively `which="."` designates the subset of function values that are displayed in the default plot. Alternatively `which` can be a character vector containing the names of columns of `expr`.

If the argument `kinks` is given, it should be a numeric vector giving the discontinuity points of the function: the value or values of the function argument at which the function is not differentiable. Differentiation will be performed separately on intervals between the discontinuity points.

If `periodic=TRUE` then the function `expr` is taken to be periodic, with period equal to the range of the function argument in `expr`. The resulting derivative is periodic.

If `periodic=FALSE` but `Dperiodic=TRUE`, then the derivative is assumed to be periodic. This would be appropriate if `expr` is the cumulative distribution function of an angular variable, for example.

### Value

Another function value table (object of class `"fv"`) of the same format.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

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

### See Also

`with.fv`, `fv.object`, `smooth.spline`

### Examples

       G <- Gest(cells)
       plot(deriv(G, which=".", spar=0.5))
       A <- pairorient(redwood, 0.05, 0.15)
       DA <- deriv(A, spar=0.6, Dperiodic=TRUE)

[Package spatstat.core version 2.0-0 Index]