Converts the dataset `X`

to a point pattern
(an object of class `"ppp"`

; see `ppp.object`

for
an overview).

This function is normally used to convert an existing point pattern
dataset, stored in another format, to the `"ppp"`

format.
To create a new point pattern from raw data such as \(x,y\)
coordinates, it is normally easier to use the creator function
`ppp`

.

The function `as.ppp`

is generic, with methods for the
classes `"ppp"`

, `"psp"`

, `"quad"`

, `"matrix"`

,
`"data.frame"`

and a default method.

The dataset `X`

may be:

an object of class `"ppp"`

an object of class `"psp"`

a point pattern object created by the spatial library

an object of class `"quad"`

representing a quadrature scheme
(see `quad.object`

)

a matrix or data frame with at least two columns

a structure with entries `x`

, `y`

which are numeric vectors
of equal length

a numeric vector of length 2, interpreted as the coordinates
of a single point.

In the last three cases, we need the second argument `W`

which is converted to a window object
by the function `as.owin`

.
In the first four cases, `W`

will be ignored.

If `X`

is a line segment pattern (an object of class `psp`

)
the point pattern returned consists of the endpoints of the segments.
If `X`

is marked then the point pattern returned will also be
marked, the mark associated with a point being the mark of the segment
of which that point was an endpoint.

If `X`

is a matrix or data frame, the first and second columns will
be interpreted as the \(x\) and \(y\) coordinates respectively.
Any additional columns will be interpreted as marks.

The argument `fatal`

indicates what to do when
`W`

is missing and `X`

contains no
information about the window. If `fatal=TRUE`

, a fatal error
will be generated; if `fatal=FALSE`

, the
value `NULL`

is returned.

In the spatial library, a point pattern is represented
in either of the following formats:

(in spatial versions 1 to 6)
a structure with entries `x`

, `y`

`xl`

, `xu`

, `yl`

, `yu`

(in spatial version 7)
a structure with entries
`x`

, `y`

and `area`

,
where `area`

is a structure with entries
`xl`

, `xu`

, `yl`

, `yu`

where `x`

and `y`

are vectors of equal length
giving the point coordinates, and `xl`

, `xu`

, `yl`

,
`yu`

are numbers giving the dimensions of a rectangular window.

Point pattern datasets can also be created by the function
`ppp`

.