pandas 熊猫：在 groupby 'date' 中删除重复项
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pandas: drop duplicates in groupby 'date'
提问by Michael Perdue
In the dataframe below, I would like to eliminate the duplicate cidvalues so the output from df.groupby('date').cid.size()matches the output from df.groupby('date').cid.nunique().
在下面的数据cid框中，我想消除重复值，以便 的输出df.groupby('date').cid.size()与df.groupby('date').cid.nunique().
I have looked at this postbut it does not seem to have a solid solution to the problem.
我看过这篇文章，但似乎没有解决问题的可靠方法。
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
Things I tried:
我尝试过的事情：
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' methoddf.groupby(('date').drop_duplicates('cid'))gives this error:AttributeError: 'str' object has no attribute 'drop_duplicates'
df.groupby([df['date']]).drop_duplicates(cols='cid')给出这个错误：AttributeError: Cannot access callable attribute 'drop_duplicates' of 'DataFrameGroupBy' objects, try using the 'apply' methoddf.groupby(('date').drop_duplicates('cid'))给出这个错误：AttributeError: 'str' object has no attribute 'drop_duplicates'
回答by ayhan
You don't need groupby to drop duplicates based on a few columns, you can specify a subset instead:
您不需要 groupby 根据几列删除重复项，您可以指定一个子集：
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
