appendData(newData, overwriteInitialSeries = true) {
    let me = this

    me.w.globals.dataChanged = true

    me.series.getPreviousPaths()

    let newSeries = me.w.config.series.slice()

    for (let i = 0; i < newSeries.length; i++) {
      if (newData[i] !== null && typeof newData[i] !== 'undefined') {
        for (let j = 0; j < newData[i].data.length; j++) {
          newSeries[i].data.push(newData[i].data[j])
        }
      }
    }
    me.w.config.series = newSeries
    if (overwriteInitialSeries) {
      me.w.globals.initialSeries = Utils.clone(me.w.config.series)
    }

    return this.update()
  }
Allows users to append Data to series.

@param {array} newData - New data in the same format as series