熊猫在多列上枢轴显示“ DataFrame的真值不明确”

Question

print a.head()
        SubjectID    form_name feature_name feature_value feature_delta
0         533  Demographic       Gender             F           0.0
1         533  Demographic          Age            65           0.0
2         533  Demographic         Race         White           0.0

This pivot, with SubjectID as the index works:

print a.pivot(index='SubjectID', columns='feature_name', values='feature_value').head()
feature_name Age Gender   Race
SubjectID                     
100256        53      M  White
100626        58      M  White
100806        66      M  White

and the same thing only with [SubjectID] as the index doesn't:

print a.pivot(index=['SubjectID'], columns='feature_name', values='feature_value').head()
ValueError: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Any ideas?

Answer 1

Function pivot doesn't support multiple columns and indexes, I think it is not implemented yet.
Issue No. 8160 and source1 .

But my error is different:

a.pivot(index=['SubjectID'], columns='feature_name', values='feature_value').head()

ValueError: Wrong number of items passed 3, placement implies 1

But:

print a.pivot(index='SubjectID', columns=['feature_name'], values='feature_value').head()

ValueError: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().