Tools for computing amortization schedules with variable interest rates are quite uncommon as opposed to those for computing their fixed interest-rate counterpart.
This code (hopefully) helps filling the gap. It includes a PDF file describing theoretical and applied amortization schedules and a MATLAB .m file functionally written as: [Amorout,T,Ratio] = amorvar(K0,Rates,Prop,Plop,Freq,Comp).
The INPUTS are:
1. K0: Initial principal borrowed
2. Rates: Tx1 time series of interest rates applied in the loan contract expressed in percent (e.g. 12.25)
3. Prop: print option to XLS file in the current MATLAB directory
4. Plop: plot option
5. Freq: yearly periodicity at end of which payment is due
6. Comp: option for computing periodic interest rate
The OUTPUT includes eight variables and two scalars:
I) Amorout: Tx8 matrix containing:
1. Tx1 vector of t.th step, t=1,...,T
2. Tx1 vector of Interest rate in %
3. Tx1 vector of Principal paid
4. Tx1 vector of Interest paid
5. Tx1 vector of Balance Outstanding
6. Tx1 vector of Payment due
7. Tx1 vector of Cumulative Payment due
8. Tx1 vector of Ratio of (7) w.r.t. K0
II) T: Total number of steps (scalar)
III) Ratio: Cumulative Payment at time T / K0 (scalar)
Enjoy and provide feedback!