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 dataset X
may be:
- an object of class
"ppp"
- an object of class
"spp"
as defined in thespatiallibrary - an object of class
"quad"
representing a quadrature scheme
(seequad.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 three cases, W
will be ignored. 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.
An spp
object is the representation of a point pattern
in the spatial library. Our implementation recognises
the following formats:
- a structure with entries
x
,y
xl
,xu
,yl
,yu
- a structure with entries
x
,y
andarea
,
wherearea
is a structure with entriesxl
,xu
,yl
,yu
(used in spatial versions 1 to 6 and version 7.1 respectively)
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. The function as.ppp
is generic, with methods for the
classes "ppp"
, "quad"
, "matrix"
, "data.frame"
and a default method.
Point pattern datasets can also be created by the function
ppp
.