spatstat.core (version 2.3-1)

objsurf: 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 dppm
objsurf(x, ..., ngrid = 32, ratio = 1.5, verbose = TRUE)
# S3 method for kppm
objsurf(x, ..., ngrid = 32, ratio = 1.5, verbose = TRUE)
# S3 method for minconfit
objsurf(x, ..., ngrid = 32, 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.

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.

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.

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.

See Also

methods.objsurf, kppm, mincontrast

Examples

# NOT RUN {
   fit <- kppm(redwood ~ 1, "Thomas")
   os <- objsurf(fit)

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