[R-sig-Geo] Grouping "linked" points

[Ben Madin]

Matthew,

You might want to look at the graphing packages for this - network, sna, igraph will all help you. What you are describing is probably best thought of as an edgelist, so if using a function such as as.network() you may need to specify that it is 'edgelist'.

example code might look like : (note I'm using a data frame for your data, and the id (row name) will become the vertex.names attribute)

> library(network)
     Classes for Relational Data
Version      1.7 created on      July 7, 2011.
copyright (c) 2005, Carter T. Butts, University of California-Irvine
                    Mark S. Handcock, University of Washington
                    David R. Hunter, Penn State University
                    Martina Morris, University of Washington
For citation information, type citation("network").
Type help("network-package") to get started.
> links <- data.frame(rbind(c(5,3),c(10,16),c(20,1),c(19,8),c(19,1),c(7,11),c(11,13),c(4,13),c(15,20),c(16,2),c(13,7),c(14,16),c(11,8),c(16,12),NULL,NULL,c(12,14),NULL,c(4,5),NULL))
> g <- network(links)
> list.vertex.attributes(g)
[1] "na"           "vertex.names"
> get.vertex.attribute(g,"vertex.names")
 [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20
> plot(g)
> ?network

cheers

Ben


On 05/08/2011, at 1:51 PM, mattc0 wrote:

> Hi,
> 
> I have a list of the links shared by n points. Each element of the list represents the ID of a point and the entries for each element indicate the ID's of the points that it is linked with. I would like to group points via their ID's based on these links. There are an unknown number of groups and some points do not share any links.
> 
> I would be grateful for any assistance in pointing me towards a solution. An example list of 20 points with two links for each point is given below.
> 
> links <- list(c(5,3),c(10,16),c(20,1),c(19,8),c(19,1),c(7,11),c(11,13),c(4,13),c(15,20),c(16,2),c(13,7),c(14,16),c(11,8),c(16,12),NULL,NULL,c(12,14),NULL,c(4,5),NULL)
> 
> Thanks in advance,
> 
> Matthew Cracknell
> PhD. Candidate
> 
> ARC Centre of Excellence in Ore Deposits
> University of Tasmania
> Private Bag 79
> Hobart, 7001
> Australia
> 
> Mob: 0409438924 
> 
> 
> 
> 	[[alternative HTML version deleted]]
> 
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo