Convert Data To Class psp

Description

Tries to coerce any reasonable kind of data to a line segment pattern (an object of class "psp") for use by the spatstat package.

Usage

  as.psp(x, ..., from=NULL, to=NULL)
  ## S3 method for class 'psp':
  as.psp(x, ..., fatal=TRUE)
  ## S3 method for class 'data.frame':
  as.psp(x, ..., window=NULL, marks=NULL, fatal=TRUE)
  ## S3 method for class 'matrix':
  as.psp(x, ..., window=NULL, marks=NULL, fatal=TRUE)
  ## S3 method for class 'owin':
  as.psp(x, ..., fatal=TRUE)
  ## Default S3 method:
  as.psp(x, ..., window=NULL, marks=NULL, fatal=TRUE)

Arguments

Details

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 columns named x0, y0, x1, y1 that will be interpreted as the coordinates of the endpoints of the segments
• a data frame or matrix with exactly 4 columns that will be interpreted as the coordinates x0, y0, x1, y1 of the endpoints of the segments
• a data frame with columns named xmid, ymid, length, angle that will be interpreted as the coordinates of the segment midpoints, the lengths of the segments, and the orientations of the segments in radians
• a structure with elements named x0, y0, x1, y1 or elements named xmid, ymid, length, angle which will be interpreted as above.
• an object of class "owin" representing a spatial window; it must be of type "rectangle" or "polygonal". The boundary edges of the window will be extracted as a line segment pattern.

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.

Value

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.

Author(s)

Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf

See Also

psp, psp.object, as.owin, owin.object

Examples

   mat <- matrix(runif(40), ncol=4)
   a <- as.psp(mat, window=owin())
   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=runifpoint(10), to=runifpoint(10))