nPlot_with_y2Axis.R

library(rCharts)
library(rjson) # required for overwrite
# load rCharts and extend Nvd3 object to allow y2Axis parameters (not implemented in rCharts yet)
nPlot <- function(x, data, ...){
  Nvd3mod <- setRefClass('Nvd3mod', contains = 'Nvd3', methods = list(
      initialize = function(){
        callSuper(); 
        LIB <<- get_lib('nvd3') # library name and url to parent library
        templates$script <<- 'NVD3.html' # chart template to include y2Axis-
        params <<- c(params, list(y2Axis = list())) 
      },
      y2Axis = function(..., replace = F){
        params$y2Axis <<- setSpec(params$y2Axis, ..., replace = replace)
      },
      getPayload = function(chartId){
        # note cannot callSuper() because of the 'toJSON' call that hardcodes the list attributes!
        data = toJSONArray(params$data)
        chart = toChain(params$chart, 'chart')
        xAxis = toChain(params$xAxis, 'chart.xAxis')
        x2Axis = toChain(params$x2Axis, 'chart.x2Axis')    
        yAxis = toChain(params$yAxis, 'chart.yAxis')
        y2Axis = toChain(params$y2Axis, 'chart.y2Axis')
        opts = toJSON(params[!(names(params) %in% c('data', 'chart', 'xAxis', 'x2Axis', 'yAxis', 'y2Axis'))])
        list(opts = opts, xAxis = xAxis, x2Axis = x2Axis, yAxis = yAxis, y2Axis = y2Axis, data = data, 
             chart = chart, chartId = chartId)
      }
    ))
  myChart <- Nvd3mod$new()
  myChart$getChartParams(x, data, ...)
  return(myChart$copy())
}