熊猫的复利资本化

Question

我正在用熊猫写一个银行存款账户的模拟。我被复利困住了（这是利息再投资的结果，所以下一个时期的利息是通过本金加上以前累积的利息来赚取的。）

到目前为止，我有以下代码：

import pandas as pd

from pandas.tseries.offsets import MonthEnd

from datetime import datetime

# Create a date range

start = '21/11/2017'

now = datetime.now()

date_rng = pd.date_range(start=start, end=now, freq='d')

# Create an example data frame with the timestamp data

df = pd.DataFrame(date_rng, columns=['Date'])

# Add column (EndOfMonth) - shows the last day of the current month

df['LastDayOfMonth'] = pd.to_datetime(df['Date']) + MonthEnd(0)

# Add columns for interest, Sasha, Artem, Total, Description

df['Debit'] = 0

df['Credit'] = 0

df['Total'] = 0

df['Description'] = ''

# Iterate through the DataFrame to set "IsItLastDay" value

for i in df:

    df['IsItLastDay'] = (df['LastDayOfMonth'] == df['Date'])

# Add the transaction of the first deposit

df.loc[df.Date == '2017-11-21', ['Debit', 'Description']] = 10000, "First deposit"

# Calculate the principal sum (It the summ of all deposits minus all withdrows plus all compaund interests)

df['Total'] = (df.Debit - df.Credit).cumsum()

# Calculate interest per day and Cumulative interest

# 11% is the interest rate per year

df['InterestPerDay'] = (df['Total'] * 0.11) / 365

df['InterestCumulative'] = ((df['Total'] * 0.11) / 365).cumsum()

# Change the order of columns

df = df[['Date', 'LastDayOfMonth', 'IsItLastDay', 'InterestPerDay', 'InterestCumulative', 'Debit', 'Credit', 'Total', 'Description']]

df.to_excel("results.xlsx")

输出文件看起来不错，但我需要以下内容：

1. “InterestCumulative”栏在每个月的最后一天添加到“Total”栏（复合利息）

2. 在每个月的开始，“InterestCumulative”列应该被清除（因为利息被添加到本金总和中）。

我怎样才能做到这一点？

Answer 1

您将需要循环，因为您的总数会根据前面的行而变化，然后会影响后面的行。因此，您当前的利息计算是错误的。total = 0cumulative_interest = 0total_per_day = []interest_per_day = []cumulative_per_day = []for day in df.itertuples():    total += day.Debit - day.Credit    interest = total * 0.11 / 365    cumulative_interest += interest    if day.IsItLastDay:        total += cumulative_interest    total_per_day.append(total)    interest_per_day.append(interest)    cumulative_per_day.append(cumulative_interest)    if day.IsItLastDay:        cumulative_interest = 0df.Total = total_per_daydf.InterestPerDay = interest_per_daydf.InterestCumulative = cumulative_per_day不幸的是，这看起来更令人困惑，但当值依赖于以前的值时就会发生这种情况。根据您的确切要求，可能有一些很好的方法可以使用数学来简化这一过程，但除此之外，这就是您所拥有的。我已将其直接写入 stackoverflow，因此它可能并不完美。