如何仅在四肢具有相同值且限制为最大出现次数时才填补数据空白？

Question

我在这里搜索了很多可以解决这个问题但找不到的答案。期望的结果是仅在四肢值相等时填充空隙，长度限制为 4 个值：

我的数据集：

0     NaN
1     NaN
2     NaN
3     5.0
4     5.0
5     NaN
6     NaN
7     5.0
8     6.0
9     NaN
10    NaN
11    NaN
12    NaN
13    NaN
14    NaN
15    5.0
16    5.0
17    NaN
18    NaN
19    6.0
20    6.0
21    NaN
22    NaN
23    NaN
24    NaN
25    5.0
26    NaN
27    NaN
28    NaN
29    NaN
30    NaN
31    NaN
32    NaN
33    5.0
34    NaN
35    NaN

期望的结果（仅在四肢值相等时填充空隙，限制为长度为 4 的空隙）：

0     NaN   # Not filled since the gap ends with 5 but this is the dataset beginning (don't know how it starts)
1     NaN   # Not filled since the gap ends with 5 but this is the dataset beginning (don't know how it starts)
2     NaN   # Not filled since the gap ends with 5 but this is the dataset beginning (don't know how it starts)
3     5.0  # Original dataset
4     5.0  # Original dataset
5     5.0    # Filled since the gap starts with 5 and ends with 5 (and is smaller than 4 values)
6     5.0    # Filled since the gap starts with 5 and ends with 5 (and is smaller than 4 values)
7     5.0  # Original dataset
8     6.0  # Original dataset
9     NaN    # Not filled since the gap starts with 6 and ends with 5
10    NaN         .
11    NaN         .
12    NaN         .
13    NaN         .
14    NaN    # Not filled since the gap starts with 6 and ends with 5
15    5.0  # Original dataset
16    5.0  # Original dataset
17    NaN    # Not filled since the gap starts with 5 and ends with 6
18    NaN    # Not filled since the gap starts with 5 and ends with 6
19    6.0  # Original dataset
20    6.0  # Original dataset
21    NaN    # Not filled since the gap starts with 6 and ends with 5
22    NaN         .
23    NaN         .
24    NaN    # Not filled since the gap starts with 6 and ends with 5
25    5.0  # Original dataset
26    5.0    # Filled since the gap starts with 5 and ends with 5
27    5.0    # Filled since the gap starts with 5 and ends with 5
28    5.0    # Filled since the gap starts with 5 and ends with 5
29    5.0    # Filled since the gap starts with 5 and ends with 5
30    NaN    # Not filled since maximum gap is 4
31    NaN    # Not filled since maximum gap is 4
32    NaN    # Not filled since maximum gap is 4
33    5.0  # Original dataset
34    NaN    # Not filled since the gap starts with 5 but this is the dataset end (don't know how it ends)
35    NaN    # Not filled since the gap starts with 5 but this is the dataset end (don't know how it ends)

Answer 1

应该是这样的：

def extremities(arr):
nones = [i for i,x in enumerate(arr) if x == None]
not_nones = [i for i,x in enumerate(arr) if x != None]
for i in nones:
    try:
        start = [x for x in not_nones if x < i][-1]
        finish = [x for x in not_nones if x > i][0]
    except:
        continue
    if arr[start] == arr[finish] and i - start < 5:
        arr[i] = arr[start]
return arr

已编辑：

抱歉，我忘了它的长度限制为 4 个值。我编辑了代码。

Answer 2

我们可以使用布尔掩码和 cumsum 来识别以相同值开始和结束的 NaN 值块，然后将这些块上的列分组并向前填充限制为 4

s = df['col']
m = s.notna()
s.mask(s[m] != s[m].shift(-1)).groupby(m.cumsum()).ffill(limit=4).fillna(s)

0     NaN
1     NaN
2     NaN
3     5.0
4     5.0
5     5.0
6     5.0
7     5.0
8     6.0
9     NaN
10    NaN
11    NaN
12    NaN
13    NaN
14    NaN
15    5.0
16    5.0
17    NaN
18    NaN
19    6.0
20    6.0
21    NaN
22    NaN
23    NaN
24    NaN
25    5.0
26    5.0
27    5.0
28    5.0
29    5.0
30    NaN
31    NaN
32    NaN
33    5.0
34    NaN
35    NaN
Name: col, dtype: float64

如何仅在四肢具有相同值且限制为最大出现次数时才填补数据空白？

How to fill data gaps only when extremities have the same value, and limited to a maximum of occurrences?

python

dataframe

pandas

fillna