# default.dummy

##### Generate a Default Pattern of Dummy Points

Generates a default pattern of dummy points for use in a quadrature scheme.

- Keywords
- spatial

##### Usage

`default.dummy(X, nx, ny, random=FALSE)`

##### Arguments

- X
- The observed data point pattern.
An object of class
`"ppp"`

or in a format recognised by`as.ppp()`

- nx, ny
- Integers specifying an
`nx`

by`ny`

rectangular array of dummy points. - random
- Logical value. If
`TRUE`

, the dummy points are randomised.

##### Details

This function provides a sensible default for the dummy points in a quadrature scheme.

A quadrature scheme consists of
the original data point pattern, an additional pattern of dummy points,
and a vector of quadrature weights for all these points.
See `quad.object`

for further information about
quadrature schemes.

If `random`

is false (the default),
then the function creates dummy points
in an `nx`

by `ny`

rectangular grid.
If `random`

is true, then the frame of the window is divided into
an `nx`

by `ny`

array of tiles, and one dummy point
is generated at random inside each tile.
In either case, the four corner points of the frame of the window
are added. Then if the window is not rectangular, any dummy points
lying outside it are deleted.
If `nx`

is missing, a default value (depending on the
data pattern `X`

) is computed by `default.ngrid`

.
If `ny`

is missing, it defaults to `nx`

.
Alternative functions for creating dummy patterns
include `corners`

,
`gridcentres`

,
`stratrand`

and
`spokes`

.

##### Value

- A point pattern (an object of class
`"ppp"`

, see`ppp.object`

) containing the dummy points.

##### See Also

`quad.object`

,
`quadscheme`

,
`corners`

,
`gridcentres`

,
`stratrand`

,
`spokes`

##### Examples

```
library(spatstat)
data(simdat)
P <- simdat
D <- default.dummy(P, 100)
plot(D)
Q <- quadscheme(P, D, "grid")
plot(union.quad(Q))
```

*Documentation reproduced from package spatstat, version 1.3-2, License: GPL version 2 or newer*