# lurking.mppm

##### Lurking Variable Plot for Multiple Point Patterns

Generate a lurking variable plot of spatial point process residuals against a covariate, for a model fitted to several point patterns.

##### Usage

```
# S3 method for mppm
lurking(object, covariate, type="eem",
…,
separate = FALSE,
plot.it = TRUE,
covname, oldstyle = FALSE, nx = 512, main="")
```

##### Arguments

- object
The fitted model. An object of class

`"mppm"`

representing a point process model fitted to several point patterns.- covariate
The covariate to be used on the horizontal axis. Either an

`expression`

which can be evaluated in the original data, or a list of pixel images, one image for each point pattern in the original data.- type
String indicating the type of residuals or weights to be computed. Choices include

`"eem"`

,`"raw"`

,`"inverse"`

and`"pearson"`

. See`diagnose.ppm`

for all possible choices.- …
Additional arguments passed to

`lurking.ppm`

, including arguments controlling the plot.- separate
Logical value indicating whether to compute a separate lurking variable plot for each of the original point patterns. If

`FALSE`

(the default), a single lurking-variable plot is produced by combining residuals from all patterns.- plot.it
Logical value indicating whether plots should be shown. If

`plot.it=FALSE`

, only the computed coordinates for the plots are returned. See*Value*.- covname
A string name for the covariate, to be used in axis labels of plots.

- oldstyle
Logical flag indicating whether error bounds should be plotted using the approximation given in the original paper (

`oldstyle=TRUE`

), or using the correct asymptotic formula (`oldstyle=FALSE`

).- nx
Integer. Number of covariate values to be used in the plot.

- main
Character string giving a main title for the plot.

##### Details

This function generates a ‘lurking variable’ plot for a
point process model fitted to several point patterns.
Residuals from the model represented by `object`

are plotted against the covariate specified by `covariate`

.
This plot can be used to reveal departures from the fitted model.

The function `lurking`

is generic. This is the method
for the class `mppm`

.
The argument `object`

must be a fitted point process model
object of class `"mppm"`

) produced by the
model-fitting algorithm `mppm`

.

##### Value

If `separate=FALSE`

(the default),
the return value is an object
belonging to the class `"lurk"`

, for which there
are methods for `plot`

and `print`

.
See `lurking`

for details of the format.

If `separate=TRUE`

, the result is a list of such objects,
and also belongs to the class `anylist`

so that it can be
printed and plotted.

##### See Also

##### Examples

```
# NOT RUN {
fit <- mppm(Points ~ Image + Group, demohyper)
lurking(fit, expression(Image), type="P")
lurking(fit, expression(Image), type="P", separate=TRUE)
# }
```

*Documentation reproduced from package spatstat, version 1.63-0, License: GPL (>= 2)*