需要画一个人形的词云，搜完之后发现wordcloud2 R语言可以有接口指定，但是没有找到js如何指定词云形状，在github上看了文档，shape的描述如下：
shape: The shape of the "cloud" to draw. Can be any polar equation represented as a callback function, or a keyword present. Available presents are circle (default), cardioid (apple or heart shape curve, the most known polar equation), diamond, square, triangle-forward, triangle, (alias of triangle-upright, pentagon, and star.
这边的polar equation我不太懂，想请问一下，如果可以指定词云形状，应该怎么调