Javasccript(D3)-日期比较返回NaN [英] Javasccript (D3) - date comparison returns NaN

问题描述

我正在使用d3并尝试比较数组中的日期.我想要得到最小和最大.

I am using d3 and trying to compare dates in an array. I want to get the minimum and maximum of it.

以下是我的数据集.

var data = [{ "date": "2016.07.19", "close": 185697.89 }, { "date": "2016.07.20", "close": 185697.89 }, { "date": "2016.07.21", "close": 186601.1 }, { "date": "2016.07.22", "close": 187273.89 }, { "date": "2016.07.25", "close": 186807.74 }];

以下是我遇到问题的代码段

The following is the code segment I am having the issue with

   max_x = 0, max_y = 0, min = 100;


  for (i = 0; i < data.length; i++) {
      max_y = Math.max(max_y, data[i].close);
      max_x = Math.max(max_x, data[i].date);
      min = Math.min(min, data[i].date);
  }

当我打印"min"变量时，它打印了"NaN".

When I printed the "min" variable, it printed "NaN".

这正在影响我的其余代码.

This is affecting the rest of my code.

有人可以指出我哪里出问题了吗? 还有其他方法可以进行日期比较吗?

Can someone point out where I've gone wrong ? Is there any other way to do date comparison ?

推荐答案

您的date值是字符串.您必须解析它们:

Your date values are strings. You have to parse them:

var parse = d3.timeParse("%Y.%m.%d");

之后，您可以使用d3.min检索最小值，使用d3.max检索最大值，或者使用d3.extent检索两者.

After that, you can retrieve the minimum with d3.min, the maximum with d3.max or both of them with d3.extent.

这是演示:

var data = [{ "date": "2016.07.19", "close": 185697.89 }, { "date": "2016.07.20", "close": 185697.89 }, { "date": "2016.07.21", "close": 186601.1 }, { "date": "2016.07.22", "close": 187273.89 }, { "date": "2016.07.25", "close": 186807.74 }];

var parse = d3.timeParse("%Y.%m.%d");

var extent = d3.extent(data.map(function(d){ return parse(d.date)}))

console.log("Minimum: " + extent[0])
console.log("Maximum: " + extent[1])

<script src="https://d3js.org/d3.v4.min.js"></script>

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