# dummy.ppm

##### Extract Dummy Points Used to Fit a Point Process Model

Given a fitted point process model, this function extracts the `dummy points' of the quadrature scheme used to fit the model.

##### Usage

`dummy.ppm(object)`

##### Arguments

- object
- fitted point process model (an object of class
`"ppm"`

).

##### Details

An object of class `"ppm"`

represents a point process model
that has been fitted to data. It is typically produced by
the model-fitting algorithm `ppm`

.
The `ppm`

algorithm approximates the pseudolikelihood
integral by a sum over a finite set of quadrature points,
which is constructed by augmenting
the original data point pattern by a set of ``dummy'' points.
The fitted model object returned by `ppm`

contains complete information about this quadrature scheme.
See `ppm`

or `ppm.object`

for further
information.
This function extracts the dummy points of the quadrature scheme.
A typical use of this function would be to count the number of dummy
points, to gauge the accuracy of the approximation to the
exact pseudolikelihood.

See `ppm.object`

for a list of all operations that can be
performed on objects of class `"ppm"`

.

##### Value

- A point pattern (object of class
`"ppp"`

).

##### See Also

##### Examples

```
data(cells)
fit <- ppm(cells, ~1, Strauss(r=0.1), rbord=0.1)
X <- dummy.ppm(fit)
X$n
# this is the number of dummy points in the quadrature scheme
```

*Documentation reproduced from package spatstat, version 1.9-1, License: GPL version 2 or newer*