d3 scale：如何使用.copy（）？ [英] d3 scale: How to use .copy()?

问题描述

我遇到了 log.copy（） ，位于 API参考中。这是什么目的？有人可以展示一个例子吗？

I came across the log.copy() in the API reference. What is the purpose of this? Can someone show an example?

如果我在一个函数中使用一个scale，可以使用 .copy 并稍后检索？

If I use a scale in one function, can I save it to a global variable by using .copy() and retrieve it later?

推荐答案

目的是， 。你基本上获得相同类型的缩放，域和范围两次，而不必设置一切两次。例如，请考虑此处的画笔演示。而不是

The purpose is, as the name suggests, to copy a scale. You essentially get the same type of scale, domain and range twice without having to set everything twice. For example, consider the brush demo here. Instead of

var x = d3.time.scale().range([0, width]),
    x2 = d3.time.scale().range([0, width]),

可以

var x = d3.time.scale().range([0, width]),
    x2 = x.copy(),

我已经做了此处。唯一的区别是代码稍短一点。

which I have done here. The only difference is that the code is very slightly shorter.

如果你只想检索一个刻度，就没有必要复制它。只有当你想要以两种不同的方式独立地修改它，你需要不同的尺度。

If you only want to retrieve a scale, there's no need to copy it. Only when you want to modify it in two different ways independently you need different scales.

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