04.course-grouping-and-sorting【分组及排序】
Introduction 介绍 Maps allow us to transform data in a DataFrame or Series one value at a time for an entire column. However, often we want to group our data, and then do something specific to the group the data is in. 映射允许我们将 DataFrame 或 Series 中的数据一次转换一整列的值。 但是，我们通常希望对数据进行分组，然后针对数据所在的组执行特定的操作。 As you’ll learn, we do this with […]