objsurf: Objective Function Surface

In spatstat.core: Core Functionality of the 'spatstat' Family

Objective Function Surface

Description

For a model that was fitted by optimisation, compute the values of the objective function in a neighbourhood of the optimal value.

Usage

objsurf(x, ...)

## S3 method for class 'dppm'
objsurf(x, ..., ngrid = 32, xlim=NULL, ylim=NULL,
                               ratio = 1.5, verbose = TRUE)

## S3 method for class 'kppm'
objsurf(x, ..., ngrid = 32, xlim=NULL, ylim=NULL,
                               ratio = 1.5, verbose = TRUE)

## S3 method for class 'minconfit'
objsurf(x, ..., ngrid = 32, xlim=NULL, ylim=NULL,
                               ratio = 1.5, verbose = TRUE)

Arguments

x	Some kind of model that was fitted by finding the optimal value of an objective function. An object of class "dppm", "kppm" or "minconfit".
...	Extra arguments are usually ignored.
ngrid	Number of grid points to evaluate along each axis. Either a single integer, or a pair of integers. For example ngrid=32 would mean a 32 * 32 grid.
xlim,ylim	Optional. Numeric vectors of length 2, specifying the limits for the two parameters to be considered.
ratio	Number greater than 1 determining the range of parameter values to be considered. If the optimal parameter value is opt then the objective function will be evaluated for values between opt/ratio and opt * ratio.
verbose	Logical value indicating whether to print progress reports.

Details

The object x should be some kind of model that was fitted by maximising or minimising the value of an objective function. The objective function will be evaluated on a grid of values of the model parameters.

Currently the following types of objects are accepted:

• an object of class "dppm" representing a determinantal point process. See dppm.

• an object of class "kppm" representing a cluster point process or Cox point process. See kppm.

• an object of class "minconfit" representing a minimum-contrast fit between a summary function and its theoretical counterpart. See mincontrast.

The result is an object of class "objsurf" which can be printed and plotted: see methods.objsurf.

Value

An object of class "objsurf" which can be printed and plotted. Essentially a list containing entries x, y, z giving the parameter values and objective function values.

There are methods for plot, print, summary, image, contour and persp.

Author(s)

\adrian

and \ege.

See Also

methods.objsurf, kppm, mincontrast

Examples

   fit <- kppm(redwood ~ 1, "Thomas")
   os <- objsurf(fit)

   if(interactive()) {
     plot(os)
     contour(os, add=TRUE)
     persp(os)
   }

spatstat.core documentation built on May 18, 2022, 9:05 a.m.