R: Extract Design Matrix from Point Process Model on a Network

model.matrix.lppm {spatstat.linnet} | R Documentation

## Extract Design Matrix from Point Process Model on a Network

### Description

Given a point process model that has been fitted to spatial point pattern data on a linear network, this function extracts the design matrix of the model.

### Usage

       ## S3 method for class 'lppm'
    model.matrix(object,
                                  data=model.frame(object, na.action=NULL),
                                  ...,
                                  keepNA=TRUE)

### Arguments

`object` | The fitted point process model. An object of class `"lppm"`.
`data` | A model frame, containing the data required for the Berman-Turner device.
`keepNA` | Logical. Determines whether rows containing NA values will be deleted or retained.
`...` | Other arguments (such as `na.action`) passed to `model.matrix.lm`.

### Details

This is a method for the generic function `model.matrix`. It extracts the design matrix of a spatial point process model on a linear network (object of class `"lppm"`).

More precisely, this command extracts the design matrix of the generalised linear model associated with a spatial point process model.

The `object` must be a fitted point process model on a network (object of class `"lppm"`) produced by the model-fitting function `lppm`. The method `model.matrix.lppm` extracts the model matrix for the GLM.

The result is a matrix, with one row for every quadrature point in the fitting procedure, and one column for every canonical covariate in the design matrix.

If there are `NA` values in the covariates, the argument `keepNA` determines whether to retain or delete the corresponding rows of the model matrix. The default `keepNA=TRUE` is to retain them. Note that this differs from the default behaviour of many other methods for `model.matrix`, which typically delete rows containing `NA`.

### Value

A matrix. Columns of the matrix are canonical covariates in the model. Rows of the matrix correspond to quadrature points in the fitting procedure (provided `keepNA=TRUE`).

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk.

### See Also

`model.matrix`, `model.images.lppm`, `lppm`

### Examples

       fit <- lppm(spiders ~ x + y)
       head(model.matrix(fit))

[Package spatstat.linnet version 2.3-1 Index]