What is the practical significance of df.DataFrame.ewm?
Hello, I met the pd. DataFrame. ewm. mean () function today, but I have done a lot of experiments and can't understand how the results are calculated.
The test code is like this:
```
x = pd.DataFrame([0.0, 1.0, 2.0])
print(pd.DataFrame.ewm(x, span=2).mean())
```
The output is like this:
```
          0
0  0.000000
1  0.750000
2  1.615385
```

I don't understand why this is the result. How did they calculate it? Can you give me some help? Thank you very much!!!