[英]Count how many times a value appears per month in dataframe
我有以下時間序列,其中包含幾年的每小時數據:
local time ghi mean
0 2013-01-01 00:00:00 0.0
1 2013-01-01 01:00:00 0.0
2 2013-01-01 02:00:00 -9999
3 2013-01-01 03:00:00 0.0
4 2013-01-01 04:00:00 0.0
.. ... ...
8754 2016-12-31 18:00:00 427.5
8755 2016-12-31 19:00:00 194.9
8756 2016-12-31 20:00:00 -9999
8757 2016-12-31 21:00:00 237.6
8758 2016-12-31 22:00:00 -9999
8759 2016-12-31 23:00:00 0.0
我需要計算值 -9999 出現的次數並按年和月分組。所需的 output 類似於:
local time ghi mean
0 2013-01 1
.. ... ...
8 2016-12 2
我試過了:
df.groupby(df["local time"].dt.strftime('%Y-%m')).df['ghi mean'].value_counts()[-9999]
但得到:
AttributeError: 'Series' object has no attribute 'df'
Boolean select,groupby sum 應該可以輕松滿足您的需求
如果df['ghi mean']
是浮點數或 integer
(df['ghi mean']==-9999).groupby(df['local time'].dt.strftime('%Y-%m')).sum()
如果您將df['ghi mean']
字符串,則
(df['ghi mean']=='-9999.0').groupby(df['local time'].dt.strftime('%Y-%m')).sum()
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