pseudoR2: Calculate Pseudo-R-Squared for Point Process Model
Description
Given a fitted point process model, calculate
the pseudo-R-squared value, which measures the
fraction of variation in the data that is explained
by the model.Usage
pseudoR2(object, ...) ## S3 method for class 'ppm':
pseudoR2(object, \dots)
## S3 method for class 'lppm':
pseudoR2(object, \dots)
Arguments
object
Fitted point process model. An object of class "ppm"
or "lppm"
.
Details
The function pseudoR2
is generic, with methods
for fitted point process models of class "ppm"
and
"lppm"
. This function computes McFadden's pseudo-Rsquared
$$R^2 = 1 - \frac{D}{D_0}$$
where $D$ is the deviance of the fitted model object
,
and $D_0$ is the deviance of the null model
(obtained by refitting object
using the trend formula ~1
).
Deviance is defined as twice the negative log-likelihood
or log-pseudolikelihood.
Examples
Run this codefit <- ppm(swedishpines ~ x+y)
pseudoR2(fit)
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