Can't render CombinedChartView

[kutran]

I am successful at using LineChartView. But when I am trying to render CombinedChartView, nothing shows up. Also, everything there is a touch event in the graph, it shows "CGAffineTransformInvert: singular matrix."

@IBOutlet weak var chartView: CombinedChartView!

var lineData = [ChartDataEntry]()
lineData.append(ChartDataEntry(x: Double(0), y: drand48()))
let lineDataSet = LineChartDataSet(values: lineData, label: "line")

var barData = [BarChartDataEntry]()
barData.append(BarChartDataEntry(x: Double(0), y: drand48()))
let barDataSet = BarChartDataSet(values: barData, label: "bar")

let combinedData = CombinedChartData(dataSets: [lineDataSet, barDataSet])
chartView.data = combinedData
charView.notifyDataSetChanged()

Am I totally missing something here?
Thank you.