# Extract.leverage.ppm

##### Extract Subset of Leverage Object

Extract a subset of a leverage map, or extract the leverage values at specified locations.

##### Usage

```
# S3 method for leverage.ppm
[(x, i, …, update=TRUE)
```

##### Arguments

- x
A leverage object (of class

`"leverage.ppm"`

) computed by`leverage.ppm`

.- i
Subset index (passed to

`[.im`

). Either a spatial window (object of class`"owin"`

) or a spatial point pattern (object of class`"ppp"`

).- …
Further arguments passed to

`[.im`

, especially the argument`drop`

.- update
Logical value indicating whether to update the internally-stored value of the mean leverage, by averaging over the specified subset.

##### Details

An object of class `"leverage.ppm"`

contains the values of the
leverage function for a point process model, computed by
`leverage.ppm`

.

This function extracts a designated subset of the leverage values, either as another leverage object, or as a vector of numeric values.

The function `[.leverage.ppm`

is a method for `[`

for the
class `"leverage.ppm"`

. The argument `i`

should be either

a spatial window (object of class

`"owin"`

) determining a region where the leverage map is required. The result will typically be another leverage map (object of class`leverage.ppm`

).a spatial point pattern (object of class

`"ppp"`

) specifying locations at which the leverage values are required. The result will be a numeric vector.

The subset operator for images, `[.im`

, is applied to
the leverage map. If this yields a pixel image, then the result of
`[.leverage.ppm`

is another leverage object. Otherwise,
a vector containing the numeric values of leverage is returned.

##### Value

Another object of class `"leverage.ppm"`

,
or a vector of numeric values of leverage.

##### See Also

##### Examples

```
# NOT RUN {
fit <- ppm(cells ~x)
lev <- leverage(fit)
b <- owin(c(0.1, 0.3), c(0.2, 0.4))
lev[b]
lev[cells]
# }
```

*Documentation reproduced from package spatstat, version 1.55-1, License: GPL (>= 2)*