使用循环获取 pandas 中每个 dataframe 条目的计算值总和（使用列数学）

Question

I have the following data frame:

For each entry of this data frame, I am looking to get the sum of log(df['s_i']/df['s_18'])*log(i/18) for i in h = [18, 56, 98, 123, 148].

I tried the following:

a = []
h = [18, 56, 98, 123, 148]

for i in df.index:
  for zi in h:
    a.append(log(df.loc[i,'s_'+str(zi)]/df.loc[i,'s_18'])*log(zi/18))
    b = sum(a)

However, it did not work. Any idea how to solve this problem? Any help would be greatly appreciated!

Answer 1

Here one thing to note use np.log<i> or math.log where is <i> base what ever you want if you don't have any custom implementation log function.
zr should to change to 18 as per your statement formula

log(df['s_i']/df['s_18'])*log(i/18) 

---

Here i am using similar layout dataframe , please check out this code:

import numpy as np
import pandas as pd

h = [18, 56, 98, 123, 148]

df = pd.DataFrame(
    data= np.arange(1, 51).reshape(10, 5),
    columns= ['s_'+str(i) for i in h]
)

# here one point should be noted that `b += sum(a)` should be in outer `for-loop` 
# otherwise as `a` grows at each iteration its `all items again added` so put
# `b += sum(a) in outer for-loop`

b = 0
for i in df.index:
    a = []
    for zi in h:
        a.append(np.log(df.loc[i,'s_'+str(zi)]/df.loc[i,'s_18'])*np.log(zi/18))
    b += sum(a)

print(b)

---

Method-2

equation = "np.log(df.loc[i,'s_'+str(j)]/df.loc[i,'s_18'])*np.log(j/18)"
b = 0
for i in df.index:
    b += sum(list(map(lambda j: eval(equation), h)))

print(b)