# 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 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).

`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 of marks
}
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

```
# 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.
```

*Documentation reproduced from package spatstat, version 1.21-0, License: GPL (>= 2)*