repricing.R

library(tidyverse)
library(FinancialMath)
library(FinCal)
library(writexl)

# loan parameters
loan_amount = 4.8e6
roi_0 = 0.0925
tenure_0 = 48

# EMI of the loan
emi_0 = FinCal::pmt(roi_0/12, 48, -loan_amount, 0, type = 0)

# get the amortization schedule
m_amort = FinancialMath::amort.table(
  Loan = loan_amount, n = 48, i = roi_0/12
)$Schedule %>% as_tibble()

# compute the impact of the rescheduling
df_amort = m_amort %>% 
  mutate(
    `Payment Dates` = 
      seq.Date(from = as.Date("2018-05-05"), as.Date("2022-04-05"), by = "month"),
    Rate = case_when(
      `Payment Dates` < as.Date("2018-07-05") ~ 0.0947,
      `Payment Dates` < as.Date("2018-09-05") ~ 0.099,
      `Payment Dates` < as.Date("2018-11-05") ~ 0.1015,
      TRUE ~ 0.1065
    ),
    `Pre-Payment Balance` = `Principal Paid` + Balance,
    `Payment Required` = `Pre-Payment Balance`*Rate/12,
    `Remaining Periods` = seq(48, 1, -1),
    `EMI (PIT)` = pmt(r = Rate/12, n = `Remaining Periods`, pv = -`Pre-Payment Balance`, 0),
    Difference = `EMI (PIT)` - Payment
  )