Python Dataframe: Calculating R^2 and RMSE Using Groupby on One Column

问题

I have the following Python dataframe:

Type    Actual  Predicted
A       4       3
A       10      18
A       13      11
B       3       10
B       4       2
B       8       33
C       20      17
C       40      33
C       87      80
C       32      30

I have the code to calculate R^2 and RMSE but I don't know how to calculate it by distinct "Type".

For now, my methodology is breaking the larger table into three smaller tables consisting of only A, B, C values and then calculating R^2 and RMSE off each smaller table...then appending them back together.

But the above method is inefficient and I believe there should be an easier way?

Below is the format I want the results to produce when things are grouped:

Type    R^2     RMSE    
A       value   value   
B       value   value   
C       value   value   

回答1:

Here is a groupby method:

import numpy as np
import pandas as pd
from sklearn.metrics import r2_score, mean_squared_error

def r2_rmse( g ):
    r2 = r2_score( g['Actual'], g['Predicted'] )
    rmse = np.sqrt( mean_squared_error( g['Actual'], g['Predicted'] ) )
    return pd.Series( dict(  r2 = r2, rmse = rmse ) )

your_df.groupby( 'Type' ).apply( r2_rmse ).reset_index()

来源：https://stackoverflow.com/questions/47914428/python-dataframe-calculating-r2-and-rmse-using-groupby-on-one-column