Tests whether a fitted point process model involves ``marks'' attached to the points.

```
# S3 method for ppm
is.marked(X, …)
```

X

Fitted point process model (object of class `"ppm"`

)
usually obtained from `ppm`

.

…

Ignored.

Logical value, equal to `TRUE`

if
`X`

is a model that was fitted to a marked point pattern dataset.

``Marks'' are observations attached to each point of a point pattern.
For example the `longleaf`

dataset contains
the locations of trees, each tree being marked by its diameter;
the `amacrine`

dataset gives the locations of cells
of two types (on/off) and the type of cell may be regarded as a mark attached
to the location of the cell.

The argument `X`

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

) typically obtained
by fitting a model to point pattern data using `ppm`

.

This function returns `TRUE`

if the *original data*
(to which the model `X`

was fitted) were a marked point pattern.

Note that this is not the same as testing whether the model involves terms that depend on the marks (i.e. whether the fitted model ignores the marks in the data). See the Examples for a trick to do this.

If this function returns `TRUE`

, the implications are
(for example) that
any simulation of this model will require simulation of random marks
as well as random point locations.

# NOT RUN { X <- lansing # Multitype point pattern --- trees marked by species # } # NOT RUN { fit1 <- ppm(X, ~ marks, Poisson()) is.marked(fit1) fit2 <- ppm(X, ~ 1, Poisson()) is.marked(fit2) ## test whether the model formula involves marks "marks" %in% spatstat.utils::variablesinformula(formula(fit2)) # Unmarked point pattern fit3 <- ppm(cells, ~ 1, Poisson()) is.marked(fit3) # FALSE # }