Pandas pd.pivot_table 给出了一个 KeyError

Question

I have a df dataframe with 4 columns 'year' , 'cath1' , 'cath2' and 'cath3' and 2000 entries corresponding to products, with corresponding year of production, and a value in each 3 categories.

I would like to create another dataframe with the same 3 category columns and compute the average value of all products for each specific year in each of these categories.

I tried with the following code but it does not work.

df1=pd.pivot_table(df,index=['year'],values=['0','1','2'],aggfunc=np.mean)

Exception has occurred: KeyError '0'

Answer 1

Your code is correct but you need to use the column name in the values.

df_pivot = pd.pivot_table(df, index=['year'], values=['cath1', 'cath2','cath3'],
                          aggfunc=np.mean)