readshpnw function

Read a network from a SpatialLines or SpatialLinesDataFrame object

A function to read a spatial network from a SpatialLines or SpatialLinesDataFrame object, and resolve it into a nodelist and edgelist for the following conversion.

readshpnw(ntdata, ELComputed=FALSE, longlat=FALSE, Detailed=FALSE, ea.prop=NULL)

Arguments

• ntdata: A SpatialLinesDataFrame or SpatialLines object

• ELComputed: If TRUE, the length of each edge will be calculated and returned

• longlat: If TRUE, distances on an ellipse with WGS84 parameters will be returned

• Detailed: If TRUE, all the vertices within the polylines of a spatial network will be recognised as nodes; if FALSE, only two endpoints of each polyline are treated as nodes

• ea.prop: A vector (of the length equalling to the number of edge attributes in in the network ntdata ) with values of 1 or 0:

  1: the corresponding column in the data frame will be kept for the new network;

  0: the corresponding column in the data frame will not be kept.

Returns

A list consisted of: - Detailed: TRUE if the output is under a Detailed mode;

• nodelist: A nodelist object

• edgelist: An edgelist object

• Edgelength: If ELComputed is TRUE, lengths of all the edges will be returned as a numeric vector; otherwise it will be NULL.

• Eadf: A data frame of attributes of the returned edges, of which the structure is a data frame with [EdgeID,(attributes inherited from the input network data)]

• nodexlist: A vector contains X-coordinates of all the nodes

• nodeylist: A vector contains Y-coordinates of all the nodes

Details

This function plays the first step to convert a spatial network (in a SpatialLines

or SpatialLinesDataFrame object) into an igraph object by returning a nodelist and edgelist .

Examples

data(ORN)
rtNEL<-readshpnw(ORN.nt)
nl<-rtNEL[[2]]
el<-rtNEL[[3]]
#Compute edge length
rtNEL<-readshpnw(ORN.nt, ELComputed=TRUE)
edgelength<-rtNEL[[4]]
eadf<-rtNEL[[5]]

Author(s)

Binbin Lu binbinlu@whu.edu.cn