pandas :在groupby'date'中删除重复项 [英] pandas: drop duplicates in groupby 'date'
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问题描述
在下面的数据框中,我想消除重复的cid
值,以便df.groupby('date').cid.size()
的输出与df.groupby('date').cid.nunique()
的输出匹配.
In the dataframe below, I would like to eliminate the duplicate cid
values so the output from df.groupby('date').cid.size()
matches the output from df.groupby('date').cid.nunique()
.
I have looked at this post but it does not seem to have a solid solution to the problem.
df = pd.read_csv('https://raw.githubusercontent.com/108michael/ms_thesis/master/crsp.dime.mpl.df')
df.groupby('date').cid.size()
date
2005 7
2006 237
2007 3610
2008 1318
2009 2664
2010 997
2011 6390
2012 2904
2013 7875
2014 3979
df.groupby('date').cid.nunique()
date
2005 3
2006 10
2007 227
2008 52
2009 142
2010 57
2011 219
2012 99
2013 238
2014 146
Name: cid, dtype: int64
我尝试过的事情:
-
df.groupby([df['date']]).drop_duplicates(cols='cid')
给出此错误:AttributeError: Cannot access callable attribute 'drop_duplicates' of 'DataFrameGroupBy' objects, try using the 'apply' method
-
df.groupby(('date').drop_duplicates('cid'))
给出此错误:AttributeError: 'str' object has no attribute 'drop_duplicates'
df.groupby([df['date']]).drop_duplicates(cols='cid')
gives this error:AttributeError: Cannot access callable attribute 'drop_duplicates' of 'DataFrameGroupBy' objects, try using the 'apply' method
df.groupby(('date').drop_duplicates('cid'))
gives this error:AttributeError: 'str' object has no attribute 'drop_duplicates'
推荐答案
您不需要groupby来基于几列删除重复项,而可以指定一个子集:
You don't need groupby to drop duplicates based on a few columns, you can specify a subset instead:
df2 = df.drop_duplicates(["date", "cid"])
df2.groupby('date').cid.size()
Out[99]:
date
2005 3
2006 10
2007 227
2008 52
2009 142
2010 57
2011 219
2012 99
2013 238
2014 146
dtype: int64
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