如何绘制绘制数学函数的自动缩放D3.js图? [英] How can I draw an autoscaling D3.js graph that plots a mathematical function?

问题描述

我有工作的jsfiddle ，它是使用JSXGraph(用于数学函数的图形工具包)制作的.我想将其移植到D3.js进行个人化，但是我很难入门.

I have a working jsfiddle that I made using JSXGraph, a graphing toolkit for mathematical functions. I'd like to port it to D3.js for personal edification, but I'm having a hard time getting started.

jsfiddle绘制了-ke(-x/T) + k的值，其中x是一个自变量，而k和t的值来自滑块.

The jsfiddle graphs the value of -ke(-x/T) + k, where x is an independent variable and the values of k and t come from sliders.

board.create('functiongraph',
  [
    // y = -k * e(-x/t) + k
    function(x) { return -k.Value()*Math.exp(-x/t.Value()) + k.Value(); },
    0
  ]
);

我最难过的三件事:

• 实际上是绘制图形及其轴-我不清楚我应该使用D3 API的许多部分中的哪个，或者应该在哪个抽象级别上进行操作.

• Actually drawing the graph and its axes - it's not clear to me which of the many parts of the D3 API I should be using, or what level of abstraction I should be operating at.

在更改滑块时重新渲染图形，并使图形知道滑块的值.

Re-rendering the graph when a slider is changed, and making the graph aware of the value of the sliders.

缩小图表，使由y = k定义的渐近线始终可见，并且不在图表的前15％之内.我现在通过以下方式执行此操作:

Zooming out the graph so that the asymptote defined by y = k is always visible and not within the top 15% of the graph. I do this now with:

function getAestheticBoundingBox() {
  var kMag = k.Value();
  var tMag = t.Value();
  var safeMinimum = 10;
  var limit = Math.max(safeMinimum, 1.15 * Math.max(k.Value(), t.Value()));

  return [0, Math.ceil(limit), Math.ceil(limit), 0];
}

我要解决这个问题的正确方法是什么?

What's the right way for me to tackle this problem?

推荐答案

我将此示例真正地放在一起 ，所以请不要在代码质量上惹恼我.但这应该为您如何在d3中执行类似操作提供一个良好的起点.我直接在d3中实现了所有内容，甚至是滑块.

I threw this example together really quick, so don't ding me on the code quality. But it should give you a good starting point for how you'd do something like this in d3. I implemented everything in straight d3, even the sliders.

正如@LarKotthoff所说，关键是您必须循环使用函数并构建数据:

As @LarKotthoff says, the key is that you have to loop your function and build your data:

// define your function
var func = function(x) {
  return -sliders.k() * Math.exp(-x / sliders.t()) + sliders.k();
},
// your step for looping function
step = 0.01;

drawPlot();

function drawPlot() {

  // avoid first callback before both sliders are created
  if (!sliders.k ||
      !sliders.t) return;

  // set your limits
  var kMag = sliders.k();
  var tMag = sliders.t();
  var safeMinimum = 10;
  var limit = Math.max(safeMinimum, 1.15 * Math.max(kMag, tMag));

  // generate your data
  var data = [];
  for (var i = 0; i < limit; i += step) {
    data.push({
      x: i,
      y: func(i)
    })
  }

  // set our axis limits
  y.domain(
    [0, Math.ceil(limit)]
  );
  x.domain(
    [0, Math.ceil(limit)]
  );

  // redraw axis
  svg.selectAll("g.y.axis").call(yAxis);
  svg.selectAll("g.x.axis").call(xAxis);

  // redraw line
  svg.select('.myLine')
    .attr('d', lineFunc(data))
}

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