[英]How can I subtract a columns from two elements of multi index?
我有一個具有多索引維度的面板數據框:國家和年份。 對於指數級別 = 0 的每個國家/地區,我只想從美國除(或減去)一些變量。
在偽代碼中
for country in countries_in_level0:
Data[‘new_variable’][country] = Data[‘variable’][country] - Data[‘variable’][‘United States’]
我試圖做的是
Data[‘new_variable’] = Data[‘variable’] - Data[‘variable’].loc[‘United States’, :]
但是我為除美國以外的每個國家都輸入了 NaN
如果需要在整個 DataFrame 中減去“United States”,可以使用xs :
Data - Data.xs(("United States"))
這里有一個例子:
arrays = [['United States', 'United States', 'baz', 'baz', 'foo', 'foo', 'qux', 'qux'],
[1, 2, 1, 2, 1, 2, 1, 2]]
tuples = list(zip(*arrays))
index = pd.MultiIndex.from_tuples(tuples, names=['country','year'])
s = pd.DataFrame(10+(10*np.random.randn(8,2)), index=index)
s
0 1
country year
United States 1 8.012399 13.287124
2 13.357553 -4.295128
baz 1 20.305391 12.381340
2 0.070968 6.314961
foo 1 25.015921 -11.577952
2 1.301654 6.000196
qux 1 4.198554 -6.915449
2 5.071788 12.423901
s - s.xs(('United States'))
0 1
country year
United States 1 0.000000 0.000000
2 0.000000 0.000000
baz 1 12.292992 -0.905785
2 -13.286585 10.610089
foo 1 17.003522 -24.865077
2 -12.055899 10.295324
qux 1 -3.813845 -20.202574
2 -8.285765 16.719028
PS:如果問題只是重新分配美國,它是
s.loc[['United States']]=1000
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