R: Objective Function Surface

objsurf {spatstat} | R Documentation

## 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, ratio = 1.5, verbose = TRUE)

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

    ## S3 method for class '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.

### 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.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au and Ege Rubak rubak@math.aau.dk.

### 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)
       }

[Package spatstat version 1.54-0 Index]