lpp {spatstat.linnet}

Create Point Pattern on Linear Network

Description

Creates an object of class "lpp" that represents a point pattern on a linear network.

Usage

lpp(X, L, ...)

Arguments

X

Locations of the points. A matrix or data frame of coordinates, or a point pattern object (of class "ppp") or other data acceptable to as.ppp.

L

Linear network (object of class "linnet").

...

Ignored.

Details

This command creates an object of class "lpp" that represents a point pattern on a linear network.

Normally X is a point pattern. The points of X should lie on the lines of L.

Alternatively X may be a matrix or data frame containing at least two columns.

• Usually the first two columns of X will be interpreted as spatial coordinates, and any remaining columns as marks.

• An exception occurs if X is a data frame with columns named x, y, seg and tp. Then x and y will be interpreted as spatial coordinates, and seg and tp as local coordinates, with seg indicating which line segment of L the point lies on, and tp indicating how far along the segment the point lies (normalised to 1). Any remaining columns will be interpreted as marks.

• Another exception occurs if X is a data frame with columns named seg and tp. Then seg and tp will be interpreted as local coordinates, as above, and the spatial coordinates x,y will be computed from them. Any remaining columns will be interpreted as marks.

If X is missing or NULL, the result is an empty point pattern (i.e. containing no points).

Value

An object of class "lpp". Also inherits the class "ppx".

Note on changed format

The internal format of "lpp" objects was changed in spatstat version 1.28-0. Objects in the old format are still handled correctly, but computations are faster in the new format. To convert an object X from the old format to the new format, use X <- lpp(as.ppp(X), as.linnet(X)).

Author(s)

Ang Qi Wei [e-mail] and Adrian Baddeley [e-mail]

See Also

Installed datasets which are "lpp" objects: chicago, dendrite, spiders.

See as.lpp for converting data to an lpp object.

See methods.lpp and methods.ppx for other methods applicable to lpp objects.

Calculations on an lpp object: intensity.lpp, distfun.lpp, nndist.lpp, nnwhich.lpp, nncross.lpp, nnfun.lpp.

Summary functions: linearK, linearKinhom, linearpcf, linearKdot, linearKcross, linearmarkconnect, etc.

Random point patterns on a linear network can be generated by rpoislpp or runiflpp.

See linnet for linear networks.

Examples

  # letter 'A' 
  v <- ppp(x=(-2):2, y=3*c(0,1,2,1,0), c(-3,3), c(-1,7))
  edg <- cbind(1:4, 2:5)
  edg <- rbind(edg, c(2,4))
  letterA <- linnet(v, edges=edg)

  # points on letter A
  xx <- list(x=c(-1.5,0,0.5,1.5), y=c(1.5,3,4.5,1.5))
  X <- lpp(xx, letterA)

  plot(X)
  X
  summary(X)

  # empty pattern
  lpp(L=letterA)