Question

我正在尝试在Charts中添加日期/字符串作为xAxis标签（标签之间必须有相等的间距）

我正在下面做，但构造函数中的x只期望有一个double。

有什么主意吗？

for i in 0..<self.grahEntries.count {
     let x1 = self.grahEntries[i].x
     let dateFormatter = DateFormatter()
     dateFormatter.dateFormat = "YYY-MM-DD HH:mm:ss"
     let date = dateFormatter.date(from: x1)
     print(date)
     let dataEntry = ChartDataEntry(x: date, y: self.grahEntries[i].y)//HERE IS MY PROBLEM!! xAxis is only double
     dataEntries.append(dataEntry)
}

 let line1 = LineChartDataSet(values: dataEntries, label: "Units Consumed")
    line1.colors = [NSUIColor.blue]
    line1.mode = .cubicBezier
    line1.cubicIntensity = 0.2


    let gradient = getGradientFilling()
    line1.fill = Fill.fillWithLinearGradient(gradient, angle: 90.0)
    line1.drawFilledEnabled = true

    let data = LineChartData()
    data.addDataSet(line1)
    mChart.data = data
    mChart.setScaleEnabled(false)
    mChart.animate(xAxisDuration: 1.5)

    mChart.xAxis.valueFormatter = DateAxisValueFormatter()
    mChart.xAxis.granularity = 1.0


    mChart.drawGridBackgroundEnabled = false
    mChart.xAxis.drawAxisLineEnabled = false
    mChart.xAxis.drawGridLinesEnabled = false
    mChart.leftAxis.drawAxisLineEnabled = true
    mChart.leftAxis.drawGridLinesEnabled = true
    mChart.rightAxis.drawAxisLineEnabled = false
    mChart.rightAxis.drawGridLinesEnabled = false
    mChart.legend.enabled = false
    mChart.xAxis.enabled = true
    mChart.leftAxis.enabled = true
    mChart.rightAxis.enabled = false

    mChart.xAxis.labelPosition = .bottom

    mChart.xAxis.drawLabelsEnabled = true
    mChart.xAxis.drawLimitLinesBehindDataEnabled = true
    mChart.xAxis.avoidFirstLastClippingEnabled = true

更新：

我确实按照@ces所说的那样准确地传播了它们，但是我仍然看不到标签。我更新了上面的代码以显示表格

Answer 1

您已经发现，您需要使用双精度（或数值）作为x的值。在此之前，我已经根据日期绘制了此图，我的方法是使用自纪元以来的秒数将日期转换为数字，并使用：-

 date.timeIntervalSince1970 / secondsPerDay

其中（足够准确）：-

let secondsPerDay = 24.0 * 3600.0

要为查看器的轴上的日期设置格式，我将使用以下格式器：-

class DateAxisValueFormatter : NSObject, IAxisValueFormatter
{
  let dateFormatter = DateFormatter()

  override init()
  {
    super.init()
    dateFormatter.dateFormat = "dd MMM"
  }

  func stringForValue(_ value: Double, axis: AxisBase?) -> String
  {
    let date = Date(timeIntervalSince1970: value * secondsPerDay)
    return dateFormatter.string(from: date)
  }
}

将我用过的值转换回正确的文本。如果您设置

lineChart.xAxis.valueFormatter = DateAxisValueFormatter()
lineChart.xAxis.granularity = 1.0

那么您只会在底部看到几天。

总而言之：

找到日期的数字转换。
使用此值
转换回格式化程序中的日期。

Answer 2

如果您希望数据均匀分布（即不代表准确的时间轴），那么答案就比较简单。

将您的for循环更改为

var dates: [String] = []
for i in 0..<self.grahEntries.count {
     let x1 = self.grahEntries[i].x
     let dateFormatter = DateFormatter()
     dateFormatter.dateFormat = "YYY-MM-DD HH:mm:ss"
     let date = dateFormatter.date(from: x1)
     dates.append(date)
     let dataEntry = ChartDataEntry(x: Double(i), y: self.grahEntries[i].y)
     dataEntries.append(dataEntry)
}

并更改

mChart.xAxis.valueFormatter = DateAxisValueFormatter(dates)

然后更改DataAxisValueFormatter以在构造函数中接受字符串数组并将其存储。更改

func stringForValue(_ value: Double, axis: AxisBase?) -> String
{
    let i = Int(value)
    return dates[i]
}

尝试在ChartDataEntry中输入日期/字符串

2 个答案: