[英]Count distinct strings in rolling window using pandas
How do I count the number of unique strings in a rolling window of a pandas dataframe? 如何计算pandas数据框滚动窗口中唯一字符串的数量?
a = pd.DataFrame(['a','b','a','a','b','c','d','e','e','e','e'])
a.rolling(3).apply(lambda x: len(np.unique(x)))
Output, same as original dataframe: 输出,与原始数据帧相同:
0
0 a
1 b
2 a
3 a
4 b
5 c
6 d
7 e
8 e
9 e
10 e
Expected: 预期:
0
0 1
1 2
2 2
3 2
4 2
5 3
6 3
7 3
8 2
9 1
10 1
I think you need first convert values to numeric - by factorize
or by rank
. 我认为你需要先将值转换为数字 - 通过factorize
或按rank
。 Also min_periods
parameter is necessary for avoid NaN
in start of column: 此外, min_periods
参数对于在列的开头避免NaN
是必需的:
a[0] = pd.factorize(a[0])[0]
print (a)
0
0 0
1 1
2 0
3 0
4 1
5 2
6 3
7 4
8 4
9 4
10 4
b = a.rolling(3, min_periods=1).apply(lambda x: len(np.unique(x))).astype(int)
print (b)
0
0 1
1 2
2 2
3 2
4 2
5 3
6 3
7 3
8 2
9 1
10 1
Or: 要么:
a[0] = a[0].rank(method='dense')
0
0 1.0
1 2.0
2 1.0
3 1.0
4 2.0
5 3.0
6 4.0
7 5.0
8 5.0
9 5.0
10 5.0
b = a.rolling(3, min_periods=1).apply(lambda x: len(np.unique(x))).astype(int)
print (b)
0
0 1
1 2
2 2
3 2
4 2
5 3
6 3
7 3
8 2
9 1
10 1
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