Class of Line Segment Patterns
"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.
An object of this class represents a two-dimensional 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).
Xis an object of type
psp, it contains the following elements:
endsdata frame with entries
x0, y0, x1, y1giving coordinates of segment endpoints
windowwindow of observation (an object of class
nnumber of line segments
marksoptional vector or data frame of marks
markformatcharacter string specifying the format of the marks;
"psp"may be created by the function
pspand 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.
There are also methods for
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.
# 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.