# deriv.fv

##### Calculate Derivative of Function Values

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

- Keywords
- spatial, nonparametric

##### Usage

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

##### 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.

##### 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 `x`

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 `x`

.

If the argument `kinks`

is given, it should be a numeric vector
giving a value or values of $x$ where the function is
not differentiable. Differentiation will be performed separately on
intervals between the discontinuity points.

##### Value

- Another function value table (object of class
`"fv"`

) of the same format.

##### See Also

##### Examples

```
data(cells)
G <- Gest(cells)
plot(deriv.fv(G, which=".", spar=0.5))
```

*Documentation reproduced from package spatstat, version 1.34-1, License: GPL (>= 2)*