d3Network: How can I relate nodes to links?

Question

I'm playing around with the d3Network package. I've run the following example from the help file. I'm sure it's very simple, but I can't figure out how it identifies what node to assign to what link.

devtools::install_github("d3Network", "christophergandrud")
library(d3Network)
library(rjson)

json_file <- "https://raw.github.com/christophergandrud/d3Network/master/JSONdata/miserables.json"
json_text <- paste(readLines(json_file), collapse = '')
MisLinks <- JSONtoDF(json_text, array = "links")
MisNodes <- JSONtoDF(json_text, array = "nodes")

d3ForceNetwork(Links = MisLinks, 
           Nodes = MisNodes, 
           Source = "source",
           Target = "target", 
           Value = "value", 
           NodeID = "name",
           Group = "group", 
           opacity = 1,
           file = "example_graph_force_directed.html")

Looking at the two data frames. The documentation says the Links data frame has to be ordered by source and the node names are in the same order.

Does this mean 'Node 1' is 'Myriel' and 'Node 2' is 'Napoleon'? If so, then where does Node 0 get named?

> head(MisLinks)
  source target value
1      1      0     1
2      2      0     8
3      3      0    10
4      3      2     6
5      4      0     1
6      5      0     1


> head(MisNodes)
             name group
1          Myriel     1
2        Napoleon     1
3 Mlle.Baptistine     1
4    Mme.Magloire     1
5    CountessdeLo     1
6        Geborand     1

Would anyone be able to explain, or show me a smaller example that might explain things?

Thanks

Answer 1

here is a simple example, created purely in R:

jjnames<-c("A","B","C","D","E","F","G","H")
mygroup<-c(1,1,1,2,2,2,2,2)
JJNodes<-data.frame( name=jjnames, group=mygroup )
jjsources<-c( 0 , 4 )
jjtargets<-c(  1,  5 )
jjvalues<-rep( c(1,2) , length(jjtargets) ) ; jjvalues<-jjvalues[1:length(jjtargets)]
JJLinks<-data.frame(source=jjsources,target=jjtargets,value=jjvalues)
d3ForceNetwork(Links = JJLinks, Nodes = JJNodes, 
           Source = "source", Target = "target", 
           Value = "value", NodeID = "name", 
           Group = "group", width = 550, height = 400, zoom=TRUE,
           opacity = 0.9)`

the links are defined by pairs of node indices. 0 => 1 links the first node with the second node.