我们这里再进行简单的区域分类，然后按照面积分别进行统计和分析，最后给出柱状直方图的图表进行展示，同时过程中我们用到了reduceregion函数来进行面积的统计，而面积统计中我们可以看到，我们用到的group来进行将统计后的结果进行以一个组的形式呈现。我们先看函数：
group(groupField, groupName)
Groups reducer records by the value of a given input, and reduces each group with the given reducer.按给定输入的值对 reducer 记录进行分组，并使用给定的 reducer 统计每个组。
Arguments:
this:reducer (Reducer):
The reducer to apply to each group, without the group field.
groupField (Integer, default: 0):
The field that contains record groups.
groupName (String, default: "group"):
The dictionary key that contains the group. Defaults to 'group'.
Returns: Reducer
var area = ee.Image.pixelArea().divide(10000).addBands(CS_2020)
.reduceRegion({
reducer: ee.Reducer.sum(),
geom