Google Earth engine -- Statistics on the frequency of land classification year by year

The functions needed in this article ：

ee.Reducer.mode(maxBuckets, minBucketWidth, maxRaw)
Create a restorer that will calculate the input pattern . For a small number of inputs （ To the most maxRaw）, The mode will be calculated directly ; For a large number of inputs , The pattern will be obtained from the histogram .

Parameters .
maxBuckets（ Integers , The default is empty. ）.
The maximum number of barrels to use when creating a histogram ; Round to 2 The power of .

minBucketWidth (Float, default: null):
Minimum width of histogram bucket , If it is empty , allows 2 To any power of .

maxRaw（ Integers , The default is empty. ）.
Before establishing the initial histogram , The number of values that need to be accumulated .

return . Reducer

ee.Reducer.frequencyHistogram()

Returns a Reducer that returns a (weighted) frequency table of its inputs.

No arguments.

Returns: Reducer

Code ：

//  Set the study area 
var s = ee.FeatureCollection("users/bqt2000204051/beijing");
var geometry = s.geometry() ; 

var exptTab = [];

//for  Cycle analysis, traverse the image data of each year and make statistics 
for