如果我有两个数据帧,其中分类列和 MultiIndex 级别不匹配,如何将它们有效地连接到单个数据帧中?
import pandas as pd
t = pd.DataFrame(data={'i1':['a','a','a','a','b','b','b','b','c','c','c','c'],
'i2':[0,1,2,3,0,1,2,3,0,1,2,3],
'x':[1.,2.,3.,4.,5.,6.,7.,8.,9.,10.,11.,12.],
'y':['x','y','x','y','x','y','x','y','x','y','x','y']})
t['i1'] = t['i1'].astype('category')
t['y'] = t['y' ].astype('category')
t.set_index(['i1','i2'], inplace=True)
t.sort_index(inplace=True)
print(t.index.levels[0]) # :-)
t2 = pd.DataFrame(data={'i1':['d','d','d','d'],
'i2':[0,1,2,3],
'x':[13.,14.,15.,16.],
'y':['x','z','x','z']})
t2['i1'] = t2['i1'].astype('category')
t2['y'] = t2['y' ].astype('category')
t2.set_index(['i1','i2'], inplace=True)
t2.sort_index(inplace=True)
pd.concat([t,t2], sort=False)
# TypeError: categories must match existing categories when appending
下面是数据帧示例:
>>> t
x y
i1 i2
a 0 1.0 x
1 2.0 y
2 3.0 x
3 4.0 y
b 0 5.0 x
1 6.0 y
2 7.0 x
3 8.0 y
c 0 9.0 x
1 10.0 y
2 11.0 x
3 12.0 y
>>> t2
x y
i1 i2
d 0 13.0 x
1 14.0 z
2 15.0 x
3 16.0 z
我有数千个数据文件和TB的数据,因此将它们转换为具有一致的类别将是一项艰巨的任务。希望可以避免这种情况。
感谢您的帮助!
t = t.reset_index()
t2 = t2.reset_index()
t3 = pd.concat([t, t2], ignore_index=True)
t3 = t3.set_index(['i1', 'i2'])
x y
i1 i2
a 0 1.0 x
1 2.0 y
2 3.0 x
3 4.0 y
b 0 5.0 x
1 6.0 y
2 7.0 x
3 8.0 y
c 0 9.0 x
1 10.0 y
2 11.0 x
3 12.0 y
d 0 13.0 x
1 14.0 z
2 15.0 x
3 16.0 z
该示例未提供原始数据的示例或其导入方式。 重新思考处理数据的方法可能更有效。
例如:
path_to_files = r'c:data*.csv'
all_files = glob.glob(path_to_files)
df = pd.concat((pd.read_csv(f) for f in all_files))
df = df.set_index(['i1', 'i2'])