R: Extract Design Matrix from Point Process Model

model.matrix.ppm {spatstat} | R Documentation

## Extract Design Matrix from Point Process Model

### Description

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

### Usage

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

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

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

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

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

### Arguments

`object` | The fitted point process model. An object of class `"ppm"` or `"kppm"` or `"dppm"` or `"ippm"` or `"lppm"`.
`data` | A model frame, containing the data required for the Berman-Turner device.
`Q` | A point pattern (class `"ppp"`) or quadrature scheme (class `"quad"`) specifying new locations where the covariates should be computed.
`keepNA` | Logical. Determines whether rows containing NA values will be deleted or retained.
`...` | Other arguments (such as `na.action`) passed to `model.matrix.lm`.
`irregular` | Logical value indicating whether to include the irregular score components.

### Details

These commands are methods for the generic function `model.matrix`. They extract the design matrix of a spatial point process model (class `"ppm"` or `"kppm"` or `"dppm"` or `"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 (object of class `"ppm"` or `"kppm"` or `"dppm"` or `"lppm"`) fitted to spatial point pattern data. Such objects are produced by the model-fitting functions `ppm`, `kppm`, `dppm` and `lppm`.

The methods `model.matrix.ppm`, `model.matrix.kppm`, `model.matrix.dppm` and `model.matrix.lppm` extract 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 constructed 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`.

The quadrature points themselves can be extracted using `quad.ppm`.

### 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`, `ppm`, `kppm`, `dppm`, `lppm`, `ippm`, `ppm.object`, `quad.ppm`, `residuals.ppm`

### Examples

       fit <- ppm(cells ~ x)
       head(model.matrix(fit))
       model.matrix(fit, Q=runifpoint(5))
       kfit <- kppm(redwood ~ x, "Thomas")
       m <- model.matrix(kfit)

[Package spatstat version 1.54-0 Index]