Javascript NVD3线图-来自JSON的自定义工具提示值

在将鼠标悬停在数据点上时，我在尝试显示部分JSON值时遇到了很多麻烦

这是我在下面使用的数据-

 var datax = [{"key":"IOVN","values":[{"x":0,"y":387.3,"z":"01640"},{"x":1,"y":387.3,"z":"01640"},{"x":2,"y":387.3,"z":"01640"},{"x":3,"y":387,"z":"01166"},{"x":4,"y":387.3,"z":"01959"},{"x":5,"y":387.3,"z":"01959"},{"x":6,"y":387.3,"z":"01959"}]},{"key":"IOVX","values":[{"x":0,"y":387.3,"z":"01640"},{"x":1,"y":387.3,"z":"01640"},{"x":2,"y":387.3,"z":"01640"},{"x":3,"y":388,"z":"01166"},{"x":4,"y":387.3,"z":"01959"},{"x":5,"y":387.3,"z":"01959"},{"x":6,"y":387.3,"z":"01959"}]}];

我希望在将鼠标悬停在显示工具提示的数据点上时显示“z”值

我尝试了各种各样的方法，但似乎在网上找不到任何东西。怎么做

有人能解释一下吗-

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这是jsfiddle-

您看过了吗？是的，这种方法可以工作，但不是按照我希望的方式，我希望它能够像我的示例中那样与惰性指南一起工作