I've been using a lot of javascript charting and visualisation libraries recently (e.g. D3, highcharts) and found that it is quite painful to get my data into the JSON structure required by each library. Since I'm doing most of the data manipulation in R anyway it makes sense to arrange the data as a nested list in R and then transform it to JSO…

dfToJSON.R

#Load libraries

library(rjson)
library(stringr)


dfToJSON<-function(df, mode='vector'){
  
  colToList<-function(x, y){
    
    col.json<-list()
    
    #Build up a list of coordinates
    
    for (i in 1:length(x)){
      
      ni<-list(x=x[i], y=y[i])
      col.json[[length(col.json)+1]]<-ni
    }
    
    return(col.json)
    
  }
  
  
  if (mode=='vector'){
    
    for.json<-list()
    
    for (j in 1:ncol(df)){
      for.json[[length(for.json)+1]]<-list(name=colnames(df)[j] , data=df[,j])
    }
    
  }
  
  if (mode=='coords') {
    
    for.json<-list()
    
    for (j in 2:ncol(df)){
      for.json[[length(for.json)+1]]<-list(name=colnames(df)[j] , data=colToList(x=df[,1], y=df[,j]))
    }
    
  }
  
  if (mode=='rowToObject') {
   
    for.json<-list()
    
    for (j in 1:nrow(df)){
      for.json[[length(for.json)+1]]<-df[j,]
    
  }
  
  jj<-toJSON(for.json)
  
  return(jj)
  
}

#example

test.set<-data.frame(x=1:20, y=rnorm(20), z=rnorm(20))
test.set.JSON.ts<-dfToJSON(test.set, 'coords')
test.set.JSON.vec<-dfToJSON(test.set, 'vector')

fileConn<-file("output.txt")
writeLines(test.set.JSON.vec, fileConn)
close(fileConn)