[R-sig-Geo] input shapefile to build graph-using R

[silverlining]

When using igraph to do network analysis- computing closeness for road
network, I confront these problems. I am trying to input shapefile data(line
and vertex), the R code is as follows:
library(igraph)
library(maptools)
pl <-
readShapeLines("H:/data/Beijing_NatrualRoads.shp",proj4string=CRS("+proj=Mercator_Auxiliary_Sphere
+datum=WGS84"))
pt <-
readShapePoints("H:/data/Beijing_NatrualRoads_ND_Junctions.shp",proj4string=CRS("+proj=Mercator_Auxiliary_Sphere
+datum=WGS84"))

Then errors occurs when trying to build graph using function
"graph.data.frame":
> g <- graph.data.frame(pl, directed=FALSE, vertices=pt)
Error in graph.data.frame(pl, directed = FALSE, vertices = pt) :
  Duplicate vertex names
Warning:
In graph.data.frame(pl, directed = FALSE, vertices = pt) :
  In `d' `NA' elements were replaced with string "NA"

Could anyone help me to solve these problems, thank you very much.



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