"""
Savings
===============================================================================
Overview
-------------------------------------------------------------------------------
The function ``savings`` computes the final balance for a savings account
with arbitrary deposits and withdrawls and variable interset rate.
Functions in this module
-------------------------------------------------------------------------------
"""
# import sys
# import os
# sys.path.insert(0, os.path.abspath('..'))
import pandas as pd
#cashflows.
from cashflows.timeseries import *
from cashflows.common import *
[docs]def savings(deposits, nrate, initbal=0):
"""
Computes the final balance for a savings account with arbitrary deposits and
withdrawls and variable interset rate.
Args:
cflo (pandas.Series): Generic cashflow.
deposits (pandas.Series): deposits to the account.
nrate (pandas.Series): nominal interest rate paid by the account.
initbal (float): initial balance of the account.
Return:
A pandas.DataFrame.
**Examples**
>>> cflo = cashflow(const_value=[100]*12, start='2000Q1', freq='Q')
>>> nrate = interest_rate([10]*12, start='2000Q1', freq='Q')
>>> savings(deposits=cflo, nrate=nrate, initbal=0) # doctest: +NORMALIZE_WHITESPACE
Beginning_Balance Deposits Earned_Interest Ending_Balance \\
2000Q1 0.000000 100.0 0.000000 100.000000
2000Q2 100.000000 100.0 2.500000 202.500000
2000Q3 202.500000 100.0 5.062500 307.562500
2000Q4 307.562500 100.0 7.689063 415.251562
2001Q1 415.251562 100.0 10.381289 525.632852
2001Q2 525.632852 100.0 13.140821 638.773673
2001Q3 638.773673 100.0 15.969342 754.743015
2001Q4 754.743015 100.0 18.868575 873.611590
2002Q1 873.611590 100.0 21.840290 995.451880
2002Q2 995.451880 100.0 24.886297 1120.338177
2002Q3 1120.338177 100.0 28.008454 1248.346631
2002Q4 1248.346631 100.0 31.208666 1379.555297
<BLANKLINE>
Nominal_Rate
2000Q1 10.0
2000Q2 10.0
2000Q3 10.0
2000Q4 10.0
2001Q1 10.0
2001Q2 10.0
2001Q3 10.0
2001Q4 10.0
2002Q1 10.0
2002Q2 10.0
2002Q3 10.0
2002Q4 10.0
>>> cflo = cashflow(const_value=[0, 100, 0, 100, 100], start='2000Q1', freq='A')
>>> nrate = interest_rate([0, 1, 2, 3, 4], start='2000Q1', freq='A')
>>> savings(deposits=cflo, nrate=nrate, initbal=1000) # doctest: +NORMALIZE_WHITESPACE
Beginning_Balance Deposits Earned_Interest Ending_Balance \\
2000 1000.000 0.0 0.00000 1000.00000
2001 1000.000 100.0 10.00000 1110.00000
2002 1110.000 0.0 22.20000 1132.20000
2003 1132.200 100.0 33.96600 1266.16600
2004 1266.166 100.0 50.64664 1416.81264
<BLANKLINE>
Nominal_Rate
2000 0.0
2001 1.0
2002 2.0
2003 3.0
2004 4.0
"""
verify_period_range([deposits, nrate])
begbal = deposits.copy()
interest = deposits.copy()
endbal = deposits.copy()
pyr = getpyr(deposits)
for time, _ in enumerate(deposits):
if time == 0:
begbal[0] = initbal
interest[0] = begbal[0] * nrate[0] / 100 / pyr
endbal[0] = begbal[0] + deposits[0] + interest[0]
else:
begbal[time] = endbal[time - 1]
interest[time] = begbal[time] * nrate[time] / 100 / pyr
if deposits[time] < 0 and -deposits[time] > begbal[time] + interest[time]:
deposits[time] = -(begbal[time] + interest[time])
endbal[time] = begbal[time] + deposits[time] + interest[time]
table = pd.DataFrame({'Beginning_Balance' : begbal,
'Deposits' : deposits,
'Nominal_Rate':nrate,
'Earned_Interest': interest,
'Ending_Balance': endbal })
return table
if __name__ == "__main__":
import doctest
doctest.testmod()