这个问题在结构上就像将行向量和列向量相乘以生成矩阵,然后对所得矩阵的行进行求和。
除了在行向量中每个元素都有两个值 A 和 B,在列向量中每个元素都有两个值 X 和 Y。并且该操作不是乘法,而是计算 A、B、X 和 Y 的函数.
下面的代码实现了目标。但是有没有一种方法可以在不使用循环并诉诸 iterrows() 的情况下做到这一点?在实际问题中,行向量有数千个元素,列向量可以有数百万个元素。
from numpy import sin, cos, exp, nan
from numpy.random import random
# Sample function that can operate on ndarrays
def myfun(a, b, x, y):
return sin(a+x), exp(b+y)
# sort of a "row vector"
df_ab = pd.DataFrame(random([2,6]),
index=['A','B'],
columns=['AB%d'%i for i in range(6)])
# sort of a "column vector"
df_xy = pd.DataFrame(random([8,2]),
columns=['X','Y'],
index=['XY%d'%i for i in range(8)])
# pre-add columns for the summarized results
df_xy['SUM_FUN0'] = nan
df_xy['SUM_FUN1'] = nan
# for each pair of values X,Y
for _, xy in df_xy.iterrows():
# calculate myfun with each pair of values A,B
funout0, funout1 = myfun(df_ab.loc['A'], df_ab.loc['B'], xy.X, xy.Y)
# summarize and store the result
xy['SUM_FUN0'] = funout0.sum()
xy['SUM_FUN1'] = funout1.sum()
最佳答案
这样的事情怎么样?我尚未测试性能,但 apply
通常比 iterrows
稍好。
import pandas as pd
from numpy import sin, cos, exp, nan, sum
from numpy.random import random
from numba import jit
# Sample function that can operate on ndarrays
@jit(nopython=True)
def myfun(a, b, x, y):
return sum(sin(a+x)), sum(exp(b+y))
# sort of a "row vector"
df_ab = pd.DataFrame(random([2,6]),
index=['A','B'],
columns=['AB%d'%i for i in range(6)])
# sort of a "column vector"
df_xy = pd.DataFrame(random([8,2]),
columns=['X','Y'],
index=['XY%d'%i for i in range(8)])
A = df_ab.loc['A'].values
B = df_ab.loc['B'].values
df_xy['SUM_FUN0'], df_xy['SUM_FUN1'] = list(zip(*df_xy.apply(lambda x: myfun(A, B, x['X'], x['Y']), axis=1)))
关于python - 将函数应用于一个 df 中的行和另一 df 中的列的所有组合,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/48542812/