# Extract.influence.ppm

##### Extract Subset of Influence Object

Extract a subset of an influence object, or extract the influence values at specified locations.

##### Usage

```
## S3 method for class 'influence.ppm':
[(x, i, ...)
```

##### Arguments

- x
- A influence object (of class
`"influence.ppm"`

) computed by`influence.ppm`

. - i
- Subset index (passed to
`[.ppp`

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

) or an integer index. - ...
- Ignored.

##### Details

An object of class `"influence.ppm"`

contains the values of the
likelihood influence for a point process model, computed by
`influence.ppm`

. This is effectively a marked point
pattern obtained by marking each of the original data points
with its likelihood influence.
This function extracts a designated subset of the influence values,
either as another influence object, or as a vector of numeric values.

The function `[.influence.ppm`

is a method for `[`

for the
class `"influence.ppm"`

. The argument `i`

should be
an index applicable to a point pattern. It may be either
a spatial window (object of class `"owin"`

)
or a sequence index.
The result will be another influence object
(of class `influence.ppm`

).

To extract the influence values as a numeric vector,
use `marks(as.ppp(x))`

.

##### Value

- Another object of class
`"influence.ppm"`

.

##### See Also

##### Examples

```
fit <- ppm(cells, ~x)
infl <- influence(fit)
b <- owin(c(0.1, 0.3), c(0.2, 0.4))
infl[b]
infl[1:5]
marks(as.ppp(infl))[1:3]
```

*Documentation reproduced from package spatstat, version 1.42-2, License: GPL (>= 2)*