将功能元素应用于两个DataFrame [英] Apply a function element-wise to two DataFrames

问题描述

如何从相同大小的DataFrame X和Y应用函数z_ij = f(x_ij, y_ij)并将结果保存到DataFrame Z?

How to apply a function z_ij = f(x_ij, y_ij) from DataFrame X and Y of the same size and save the result to DataFrame Z?

推荐答案

这取决于您具有哪种功能，已经针对数据帧将许多功能矢量化了，例如+-*/等，因此对于这些功能，您只需执行Z = X + Y或Z = X - Y等.

It depends on what kind of function you have, a lot of functions have already been vectorized for data frame, such as +-*/ etc, so for these functions, you can simply do Z = X + Y or Z = X - Y etc.

对于更通用的功能，可以使用numpy.vectorize对其进行矢量化处理，然后应用于两个数据帧:

For a more general function, you can use numpy.vectorize to make a vectorized version of it and then apply to two data frames:

import numpy as np
import pandas as pd

X = pd.DataFrame([[1,2], [3,4]])
Y = pd.DataFrame([[2,1], [3,3]])
​
def f(x, y):                      # this is a demo function that takes in two ints and 
    return str(x) + str(y)        # concatenate them as str
​
vecF = np.vectorize(f)            # vectorize the function with numpy.vectorize
​
X
#   0   1
#0  1   2
#1  3   4

Y
#   0   1
#0  2   1
#1  3   3

pd.DataFrame(vecF(X, Y))          # apply the function to two data frames

#    0   1
#0  12  21
#1  33  43

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