如何在chartjs中绘制多个时间序列，其中每个时间序列都有不同的时间

2022-01-22 00:00:00 python javascript chart.js

例如，我有两个时间序列:

I have two time series for example:

s1:
  2017-01-06 18:39:30    100
  2017-01-07 18:39:28    101

和

s2:
2017-01-07 18:00:00     90
2017-01-08 18:00:00    105

我想在 Chartjs 图表中绘制这些，但是 Chartjs 似乎只需要一个 x 轴数组(或 Chartjs 术语中的标签).

I want to plot these in a Chartjs chart, however it seems that Chartjs only takes one x-axis array (or label in Chartjs terminology).

所以我的问题是绘制这两者的最佳方法是什么?

我的方法是编写一个函数(在 python 中，尽管语言对于这部分并不重要)，它遍历两个时间序列并创建 3 个新数组，其格式显然是 Chartjs 需要基于第一个示例此处:https://www.sitepoint.com/introduction-chart-js-2-0-six​​-examples/

My approach was to write a function (in python, although the language doesn't really matter for this part) that iterates through both time series and creates 3 new arrays which is in the format apparently Chartjs needs based off the 1st example here: https://www.sitepoint.com/introduction-chart-js-2-0-six-examples/

算法(在 sudo 代码中)如下所示:

The algorithm (in sudo code) goes like:

    # inputs are initial time series s1 and s2
    y1 = [] # to hold new s1 data values
    y2 = [] # to hold new s2 data values
    x  = [] # to hold times

    # iterate through longest series s1 or s2
    if s1[idx].time > s2[idx].time
      x.append(s1[idx].time)
      y1.append(s1[idx].data)
      # y2 appends the linear interpolation of 
      # of closest y2 points

    if (s1[idx].time < s2[idx].time)
      x.append(s2[idx].time)
      # opposite of above. ie. swap y1<->y2, s1->s2

    else # they have the same time
      x.append(s1[idx].time)
      y1.append(s1[idx].data)
      y2.append(s2[idx].data)

当数据用完较短的系列时，还有其他几个条件检查，但这是主要逻辑.之后我有 3 个数组，我现在可以通过一个时间/标签数组/x 轴和两个数据数组将它们添加到图表 js.然而，这似乎比我认为这个用例的常见程度要复杂得多.非常感谢任何帮助或建议.

There are a couple other conditional checks for when data runs out of the shorter series but that is the main logic. After which I have 3 arrays that I can now add to chart js via one time/label array/x-axis and two data arrays. However this seems WAY more complicated than it should be considering how common I assume this use case is. Any help or advice is greatly appreciated.

推荐答案

在 ChartJS 中，标签是一个 类别笛卡尔坐标轴.由于您在代码中提到了线性插值，我假设像 2017-01-06 18:39:30 这样的字符串不是类别，它们代表 x 轴的数值.所以我们需要通知 ChartJS x 轴上的字符串实际上是时间.我们在比例选项中执行此操作.

In ChartJS, label is a Category Cartesian Axis. Since you mentioned linear interpolation in your code, I assume the strings like 2017-01-06 18:39:30 are not categories, they represent the numeric values of the x-axis. So we need to inform ChartJS that the strings in the x axis are actually time. We do this in the scale options.

var s1 = {
  label: 's1',
  borderColor: 'blue',
  data: [
    { x: '2017-01-06 18:39:30', y: 100 },
    { x: '2017-01-07 18:39:28', y: 101 },
  ]
};

var s2 = {
  label: 's2',
  borderColor: 'red',
  data: [
    { x: '2017-01-07 18:00:00', y: 90 },
    { x: '2017-01-08 18:00:00', y: 105 },
  ]
};

var ctx = document.getElementById('myChart').getContext('2d');
var chart = new Chart(ctx, {
  type: 'line',
  data: { datasets: [s1, s2] },
  options: {
    scales: {
      xAxes: [{
        type: 'time'
      }]
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.20.1/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.1/Chart.min.js"></script>
<canvas id="myChart"></canvas>

您可以在 Chart.js 文档中找到更多信息.

You can find more information in Chart.js documentation.

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