psp.object
Class of Line Segment Patterns
A class "psp"
to represent a spatial pattern of
line segments in the plane.
Includes information about the window in which the
pattern was observed. Optionally includes marks.
Details
An object of this class represents a twodimensional pattern of line segments. It specifies
the locations of the line segments (both endpoints)
the window in which the pattern was observed
optionally, a ``mark'' attached to each line segment (extra information such as a type label).
If X
is an object of type psp
,
it contains the following elements:
ends 
data frame with entries x0, y0, x1, y1 
giving coordinates of segment endpoints  
window 
window of observation 
(an object of class owin ) 

n 
number of line segments 
marks 
optional vector or data frame of marks 
markformat 
character string specifying the format of the 
Users are strongly advised not to manipulate these entries directly.
Objects of class "psp"
may be created by the function
psp
and converted from other types of data by the function
as.psp
.
Note that you must always specify the window of observation;
there is intentionally no default action of ``guessing'' the window
dimensions from the line segments alone.
Subsets of a line segment pattern may be obtained by the functions
[.psp
and clip.psp
.
Line segment pattern objects can be plotted just by typing plot(X)
which invokes the plot
method for line segment pattern objects,
plot.psp
. See plot.psp
for further information.
There are also methods for summary
and print
for line segment patterns. Use summary(X)
to see a useful description
of the data.
Utilities for line segment patterns include
midpoints.psp
(to compute the midpoints of each segment),
lengths.psp
, (to compute the length of each segment),
angles.psp
, (to compute the angle of orientation of
each segment), and
distmap.psp
to compute the distance map of a
line segment pattern.
See Also
Examples
# NOT RUN {
# creating
a < psp(runif(20),runif(20),runif(20),runif(20), window=owin())
# converting from other formats
a < as.psp(matrix(runif(80), ncol=4), window=owin())
a < as.psp(data.frame(x0=runif(20), y0=runif(20),
x1=runif(20), y1=runif(20)), window=owin())
# clipping
w < owin(c(0.1,0.7), c(0.2, 0.8))
b < clip.psp(a, w)
b < a[w]
# the last two lines are equivalent.
# }