R networkD3 package: node coloring in simpleNetwork()

Question

The networkD3 package (see here and here) allows a user to create simple interactive networks:

# Load package
library(networkD3)

# Create fake data
src <- c("A", "A", "A", "A",
        "B", "B", "C", "C", "D")
target <- c("B", "C", "D", "J",
            "E", "F", "G", "H", "I")
networkData <- data.frame(src, target)

# Plot
simpleNetwork(networkData)

Is there a way to specify that I want all elements in the src vector to be a certain color, while allowing all the elements in the target vector to be a different color? This would allow me to visually distinguish src nodes from target nodes in the network.

This functionality doesn't seem to be currently supported in simpleNetwork() (but I'm hoping somebody could help me out with a homebrew script):

A similar but not related question was asked here.

Answer 1

Here's how to control colour of nodes with forceNetwork. Notice this still won't tell you the direction of the links because some nodes are source for some links and target for others - so you'll need to rethink that logic somehow. But anyway, here's controlling colour of nodes.

# Load package
library(networkD3)
library(dplyr) # to make the joins easier

# Create fake data
src <- c("A", "A", "A", "A",
         "B", "B", "C", "C", "D")
target <- c("B", "C", "D", "J",
            "E", "F", "G", "H", "I")
networkData <- data.frame(src, target, stringsAsFactors = FALSE)

nodes <- data.frame(name = unique(c(src, target)), stringsAsFactors = FALSE)
nodes$id <- 0:(nrow(nodes) - 1)


# create a data frame of the edges that uses id 0:9 instead of their names
edges <- networkData %>%
   left_join(nodes, by = c("src" = "name")) %>%
   select(-src) %>%
   rename(source = id) %>%
   left_join(nodes, by = c("target" = "name")) %>%
   select(-target) %>%
   rename(target = id)

edges$width <- 1

# make a grouping variable that will match to colours
nodes$group <- ifelse(nodes$name %in% src, "lions", "tigers")

# simple with default colours
forceNetwork(Links = edges, Nodes = nodes, 
             Source = "source",
             Target = "target",
             NodeID ="name",
             Group = "group",
             Value = "width",
             opacity = 0.9,
             zoom = TRUE)

# control colours with a JS ordinal scale
# edited 20 May 2017 with updated code from Renal Chesak's answer:
ColourScale <- 'd3.scaleOrdinal()
            .domain(["lions", "tigers"])
           .range(["#FF6900", "#694489"]);'

forceNetwork(Links = edges, Nodes = nodes, 
             Source = "source",
             Target = "target",
             NodeID ="name",
             Group = "group",
             Value = "width",
             opacity = 0.9,
             zoom = TRUE,
             colourScale = JS(ColourScale))

Answer 2

Peter Ellis' answer does the job, but this is an alternate approach, which imho is bit more concise and easier to understand...

(Also, it should be noted that nodes can be in both the source and the target vectors at the same time, in which case, which color they should be, given your specification, is uncertain.)

library(networkD3)

src <- c("A", "A", "A", "A", "B", "B", "C", "C", "D")
target <- c("B", "C", "D", "J", "E", "F", "G", "H", "I")
networkData <- data.frame(src, target, stringsAsFactors = FALSE)

# make a nodes data frame out of all unique nodes in networkData
nodes <- data.frame(name = unique(c(networkData$src, networkData$target)))

# make a group variable where nodes in networkData$src are identified
nodes$group <- nodes$name %in% networkData$src

# make a links data frame using the indexes (0-based) of nodes in 'nodes'
links <- data.frame(source = match(networkData$src, nodes$name) - 1,
                    target = match(networkData$target, nodes$name) - 1)

forceNetwork(Links = links, Nodes = nodes, Source = "source",
             Target = "target", NodeID ="name", Group = "group",
             opacity = 1, opacityNoHover = 1)