# vcov.mppm

##### Calculate Variance-Covariance Matrix for Fitted Multiple Point Process Model

Given a fitted multiple point process model, calculate the variance-covariance matrix of the parameter estimates.

##### Usage

```
# S3 method for mppm
vcov(object, ..., what="vcov", err="fatal")
```

##### Arguments

- object
A multiple point process model (object of class

`"mppm"`

).- …
Arguments recognised by

`vcov.ppm`

.- what
Character string indicating which quantity should be calculated. Options include

`"vcov"`

for the variance-covariance matrix,`"corr"`

for the correlation matrix, and`"fisher"`

for the Fisher information matrix.- err
Character string indicating what action to take if an error occurs. Either

`"fatal"`

,`"warn"`

or`"null"`

.

##### Details

This is a method for the generic function `vcov`

.

The argument `object`

should be a fitted multiple point process
model (object of class `"mppm"`

) generated by `mppm`

.

The variance-covariance matrix of the parameter estimates is computed using asymptotic theory for maximum likelihood (for Poisson processes) or estimating equations (for other Gibbs models).

If `what="vcov"`

(the default), the variance-covariance matrix
is returned.
If `what="corr"`

, the variance-covariance matrix is normalised
to yield a correlation matrix, and this is returned.
If `what="fisher"`

, the Fisher information matrix is returned instead.

In all three cases, the rows and columns of the matrix correspond
to the parameters (coefficients) in the same order as in
`coef{model}`

.

If errors or numerical problems occur, the
argument `err`

determines what will happen. If
`err="fatal"`

an error will occur. If `err="warn"`

a warning will be issued and `NA`

will be returned.
If `err="null"`

, no warning is issued, but `NULL`

is returned.

##### Value

A numeric matrix (or `NA`

or `NULL`

).

##### Error messages

An error message that reports
*system is computationally singular* indicates that the
determinant of the Fisher information matrix of one of the models
was either too large or too small for reliable numerical calculation.
See `vcov.ppm`

for suggestions on how to handle this.

##### References

Baddeley, A., Rubak, E. and Turner, R. (2015)
*Spatial Point Patterns: Methodology and Applications with R*.
London: Chapman and Hall/CRC Press.

##### See Also

##### Examples

```
# NOT RUN {
fit <- mppm(Wat ~x, data=hyperframe(Wat=waterstriders))
vcov(fit)
# }
```

*Documentation reproduced from package spatstat, version 1.56-1, License: GPL (>= 2)*