SpatialGraph (version 1.0-4)

sl2sg: Map a SpatialLinesDataFrame into a SpatialGraph

Description

This function is the major workhorse to map an input SpatialLinesDataFrame, as defined in the package sp, into a SpatialGraph by using the spatial connectivity. Input is first exploded by using explodeSLDF, and then all vertices in the SpatialGraph are automatically generated according to crossings in the input polylines.

Usage

sl2sg(SL, clipd = NULL, getdist = TRUE, getpath = FALSE)

Value

A SpatialGraph

Arguments

SL

SpatialLinesDataFrame as defined in package sp

clipd

distance threshold for clipping features, If NULL, a value of 1.0E-04 of the domain side size is used

getdist

calculate the dist slot in the returned SpatialGraph

getpath

calculate the path slot in the returned SpatialGraph

Author

Javier Garcia-Pintado, e-mail:

Details

A SpatialGraph is generated

Examples

  #  x   y
  # create list of Line objects
 if (1 > 2) {
  library(sp)
  library(SpatialGraph)
  zz <- list()
  zz[[1]] <- Line(matrix(
   c(661750, 4229150,
     662650, 4229450,
     663550, 4227650,
     663550, 4226850), ncol=2, byrow=TRUE))
  zz[[2]] <- Line(matrix(
   c(660250, 4229650,
     661050, 4226450,
     662550, 4225350,
     664850, 4225850,
     664650, 4229150,
     662350, 4228850), ncol=2, byrow=TRUE))
  # upgrade Line as Lines
  for (i in 1:length(zz)) {
    zz[[i]] <- Lines(list(zz[[i]]), ID=i)
  }
  # as SpatialLines
  SL <- sp::SpatialLines(zz)
  # as SpatialGraph including path calculation
  SG <- sl2sg(SL, getpath=TRUE) 

  plot(SL, axes=TRUE)  
  points(SG@v, cex=2)
  lines(SG@e, lwd=2)
  points(SG@v, cex=2, col='grey', pch=19)
  text(SG@v, labels=SG@v$ID)
  # label edges and directions
  textSGe(SG)
  # show a distance matrix between nodes
  SG@dist
  # show path from node 1 to 3
  SG@path[1,3]
 }