This is the `plot`

method for the class `"cdftest"`

.
An object of this class represents the outcome of
a spatial distribution test, computed by `cdf.test`

,
and based on either the Kolmogorov-Smirnov,
Cramer-von Mises
or Anderson-Darling test.

If `style="cdf"`

(the default),
the plot displays the two cumulative distribution functions
that are compared by the test: namely the empirical cumulative distribution
function of the covariate at the data points, and the predicted
cumulative distribution function of the covariate under the model,
both plotted against the value of the covariate. The
Kolmogorov-Smirnov test statistic (for example)
is the maximum vertical separation
between the two curves.

If `style="PP"`

then the P-P plot is drawn. The
\(x\) coordinates of the plot are cumulative
probabilities for the covariate under the model.
The \(y\) coordinates are cumulative probabilities
for the covariate at the data points. The diagonal line
\(y=x\) is also drawn for reference. The Kolmogorov-Smirnov
test statistic is the maximum vertical separation
between the P-P plot and the diagonal reference line.

If `style="QQ"`

then the Q-Q plot is drawn. The
\(x\) coordinates of the plot are quantiles
of the covariate under the model.
The \(y\) coordinates are quantiles of the
covariate at the data points. The diagonal line
\(y=x\) is also drawn for reference. The Kolmogorov-Smirnov
test statistic cannot be read off the Q-Q plot.