as.psp | R Documentation |
Tries to coerce any reasonable kind of data object to a line segment pattern
(an object of class "psp"
)
for use by the spatstat package.
as.psp(x, ..., from=NULL, to=NULL) ## S3 method for class 'psp' as.psp(x, ..., check=FALSE, fatal=TRUE) ## S3 method for class 'data.frame' as.psp(x, ..., window=NULL, marks=NULL, check=spatstat.options("checksegments"), fatal=TRUE) ## S3 method for class 'matrix' as.psp(x, ..., window=NULL, marks=NULL, check=spatstat.options("checksegments"), fatal=TRUE) ## Default S3 method: as.psp(x, ..., window=NULL, marks=NULL, check=spatstat.options("checksegments"), fatal=TRUE)
x |
Data which will be converted into a line segment pattern |
window |
Data which define a window for the pattern. |
... |
Ignored. |
marks |
(Optional) vector or data frame of marks for the pattern |
check |
Logical value indicating whether to check the validity of the data, e.g. to check that the line segments lie inside the window. |
fatal |
Logical value. See Details. |
from,to |
Point patterns (object of class |
Converts the dataset x
to a line segment pattern
(an object of class "psp"
; see psp.object
for
an overview).
This function is normally used to convert an existing line segment pattern
dataset, stored in another format, to the "psp"
format.
To create a new point pattern from raw data such as x,y
coordinates, it is normally easier to use the creator function
psp
.
The dataset x
may be:
an object of class "psp"
a data frame with at least 4 columns
a structure (list) with elements named x0, y0,
x1, y1
or elements named xmid, ymid, length, angle
and possibly a fifth element named marks
If x
is a data frame the interpretation of its columns is
as follows:
If there are columns named x0, y0, x1, y1
then these
will be interpreted as the coordinates of the endpoints of
the segments and used to form the ends
component of
the psp
object to be returned.
If there are columns named xmid, ymid, length, angle
then these will be interpreted as the coordinates of the segment
midpoints, the lengths of the segments, and the orientations
of the segments in radians and used to form the ends
component of the psp
object to be returned.
If there is a column named marks
then this will
be interpreted as the marks of the pattern provided that
the argument marks
of this function is NULL
.
If argument marks
is not NULL
then the value
of this argument is taken to be the marks of the pattern and
the column named marks
is ignored (with a warning).
In either case the column named marks is deleted and omitted
from further consideration.
If there is no column named marks
and if the marks
argument of this function is NULL
, and if after
interpreting 4 columns of x
as determining the ends
component of the psp
object to be returned, there remain
other columns of x
, then these remaining columns will be
taken to form a data frame of marks for the psp
object
to be returned.
If x
is a structure (list) with elements named x0,
y0, x1, y1, marks
or xmid, ymid, length, angle, marks
,
then the element named marks
will be interpreted as the
marks of the pattern provide that the argument marks
of
this function is NULL
. If this argument is non-NULL
then it is interpreted as the marks of the pattern and the element
marks
of x
is ignored — with a warning.
Alternatively, you may specify two point patterns
from
and to
containing the first and second endpoints
of the line segments.
The argument window
is converted to a window object
by the function as.owin
.
The argument fatal
indicates what to do when
the data cannot be converted to a line segment pattern.
If fatal=TRUE
, a fatal error
will be generated; if fatal=FALSE
, the
value NULL
is returned.
The function as.psp
is generic, with methods for the
classes "psp"
, "data.frame"
, "matrix"
and a default method.
Point pattern datasets can also be created by the function
psp
.
An object of class "psp"
(see psp.object
)
describing the line segment pattern and its window of observation.
The value NULL
may also be returned; see Details.
If only a proper subset of the names x0,y0,x1,y1
or
xmid,ymid,length,angle
appear amongst the names of the
columns of x
where x
is a data frame, then these
special names are ignored.
For example if the names of the columns were
xmid,ymid,length,degrees
, then these columns would be
interpreted as if the represented x0,y0,x1,y1
in that order.
Whether it gets used or not, column named marks
is
always removed from x
before any attempt to form the
ends
component of the psp
object that is returned.
.
psp
,
psp.object
,
as.owin
,
owin.object
.
See edges
for extracting the edges of a polygonal window
as a "psp"
object.
mat <- matrix(runif(40), ncol=4) mx <- data.frame(v1=sample(1:4,10,TRUE), v2=factor(sample(letters[1:4],10,TRUE),levels=letters[1:4])) a <- as.psp(mat, window=owin(),marks=mx) mat <- cbind(as.data.frame(mat),mx) b <- as.psp(mat, window=owin()) # a and b are identical. stuff <- list(xmid=runif(10), ymid=runif(10), length=rep(0.1, 10), angle=runif(10, 0, 2 * pi)) a <- as.psp(stuff, window=owin()) b <- as.psp(from=runifrect(10), to=runifrect(10))
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