Ios Swift图表删除数据

我使用is-Charts，在UIView中我有按钮（1,2,3,4）和带图表的UIView

我希望如果按1键-删除旧数据行并用新数据显示新数据^

func populateData(withCount countA: [Double], countB: [Double]) {
  for index in 0..<countB.count{
            let dataEntry = ChartDataEntry(x: countB[index], y: countA[index])
            values.append(dataEntry)
        }
 let set = LineChartDataSet(values: values, label: "")
        set.mode = .cubicBezier
        set.cubicIntensity = 0.2
        set.drawCirclesEnabled = true
        set.lineWidth = 2.7
        set.circleRadius = 2.8
        set.setCircleColor(.green)
        set.setColor(#colorLiteral(red: 0.3176470588, green: 0.9960784314, blue: 0.6549019608, alpha: 1))
        set.fillColor = .green
        set.fillAlpha = 1.0
        set.drawHorizontalHighlightIndicatorEnabled = false
        set.drawVerticalHighlightIndicatorEnabled = false
         let gradientColors = [UIColor.cyan.cgColor, UIColor.clear.cgColor] as CFArray 
        let colorLocations:[CGFloat] = [1.0, 0.0] 
        let gradient = CGGradient.init(colorsSpace: CGColorSpaceCreateDeviceRGB(), colors: gradientColors, locations: colorLocations
        set.fill = Fill.fillWithLinearGradient(gradient!, angle: 90.0) 
        set.drawFilledEnabled = true 


        let data = LineChartData(dataSet: set)
        data.setDrawValues(false)
        chartView.data = data
    }

在按钮1中：

 chartView.clear()
 populateData(withCount: a, countB: b)

在按钮2中：

chartView.clear()
 populateData(withCount: c, countB: d)

但它不起作用，数据不变，只添加和显示两行

---

如何删除和放置新数据？

在填充数据之前，请执行以下操作：

values = []

顺便说一下，我会这样写：

func populateData(withCount countA: [Double], countB: [Double]) {
  values = []
  for index in 0..<countB.count{
      let dataEntry = ChartDataEntry(x: countB[index], y: countA[index])
      values.append(dataEntry)
        }
...

func填充数据（使用count countA:[Double]，countB:[Double]）{
值=[]
对于0中的索引…非常感谢！
func populateData(withCount countA: [Double], countB: [Double]) {
  values = []
  for index in 0..<countB.count{
      let dataEntry = ChartDataEntry(x: countB[index], y: countA[index])
      values.append(dataEntry)
        }
...