[英]Dropping rows from dataframe based on the value of the previous row
I have a dataframe like the following:我有一个 dataframe 如下所示:
2018-10-16 15:15:00 1810.388020
2018-10-16 15:20:00 1813.299467
2018-10-16 15:25:00 1812.550495
2018-10-16 15:45:00 18140.981919
2018-10-16 15:35:00 1814.473347
2018-10-16 15:40:00 1816.349779
2018-10-16 15:45:00 740.981919
2018-10-16 15:50:00 1819.066781
2018-10-16 15:55:00 1820.333191
I need a dataframe like the following:我需要一个 dataframe,如下所示:
2018-10-16 15:15:00 1810.388020
2018-10-16 15:20:00 1813.299467
2018-10-16 15:25:00 1812.550495
2018-10-16 15:35:00 1814.473347
2018-10-16 15:40:00 1816.349779
2018-10-16 15:50:00 1819.066781
2018-10-16 15:55:00 1820.333191
That is:For every row having more value than 1.5 the previous row value or less than 0.5 the previous row value, drop it即:对于每一行的值大于前一行值的 1.5 或小于前一行值的 0.5,将其删除
Idea is compare previous and also next values, chaining by |
想法是比较前一个值和下一个值,通过|
链接for bitwise OR
and last by bitwise AND
with filtering by boolean indexing
:对于按位OR
和最后按位AND
并通过boolean indexing
过滤:
m11 = df['col'] > df['col'].shift(-1) * 0.5
m12 = df['col'] > df['col'].shift() * 0.5
m21 = df['col'] < df['col'].shift(-1) * 1.5
m22 = df['col'] < df['col'].shift() * 1.5
df = df[(m11 | m12) & (m21 | m22)]
print (df)
col
2018-10-16 15:15:00 1810.388020
2018-10-16 15:20:00 1813.299467
2018-10-16 15:25:00 1812.550495
2018-10-16 15:35:00 1814.473347
2018-10-16 15:40:00 1816.349779
2018-10-16 15:50:00 1819.066781
2018-10-16 15:55:00 1820.333191
Detail :详情:
df['m11'] = df['col'] > df['col'].shift(-1) * 0.5
df['m12'] = df['col'] > df['col'].shift() * 0.5
df['m21'] = df['col'] < df['col'].shift(-1) * 1.5
df['m22'] = df['col'] < df['col'].shift() * 1.5
df['m1'] = (df['m11'] | df['m12'])
df['m2'] = (df['m21'] | df['m22'])
df['mask'] = df['m1'] & df['m2']
print (df)
col m11 m12 m21 m22 m1 m2 \
2018-10-16 15:15:00 1810.388020 True False True False True True
2018-10-16 15:20:00 1813.299467 True True True True True True
2018-10-16 15:25:00 1812.550495 False True True True True True
2018-10-16 15:45:00 18140.981919 True True False False True False
2018-10-16 15:35:00 1814.473347 True False True True True True
2018-10-16 15:40:00 1816.349779 True True False True True True
2018-10-16 15:45:00 740.981919 False False True True False True
2018-10-16 15:50:00 1819.066781 True True True False True True
2018-10-16 15:55:00 1820.333191 False True False True True True
mask
2018-10-16 15:15:00 True
2018-10-16 15:20:00 True
2018-10-16 15:25:00 True
2018-10-16 15:45:00 False
2018-10-16 15:35:00 True
2018-10-16 15:40:00 True
2018-10-16 15:45:00 False
2018-10-16 15:50:00 True
2018-10-16 15:55:00 True
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