Finance App TVM with irregular cash flows

[Stefan Falk]

Hello everybody!

I am still in the process of learning the HP Prime with its overwhelming set of functionality. Up to now, I could not figure out how to calculate the loan for a bought house with additional payments. The finance app calculates well using just the monthly paid amount, but how do I calculate the plan if we pay additional amounts at different times (we are allowed to pay up to additional 5% of the total amount each year)?

Best Regards,
Stefan

[roadrunner]

I would do something like that with the spreadsheet app; like the one attached.

-road


  loan_example.hpappdir.zip (Size: 13.63 KB / Downloads: 8)

[Stefan Falk]

Thank you very much, roadrunner!

I'll try to get the hpapp into my prime.

Btw, do I remember correctly that the good old HP-92 desktop calculator could handle that, or was that "just" irregular cash flows in bond calculations?

Thanks again,
Stefan

[Stefan Falk]

Hello roadrunner again,

I tried your app and it seems to work fine. I had made an Excel sheet for the calculations, because the dates at which we paid the additional 5% varied from year to year.

Isn't there some built-in function accepting some array of dates and amounts in addition to the usual suspects such as PV, FW and so on? I could not find one yet.

Best Regards,
Stefan

[Albert Chan]

Hi, Stefan Falk

Welcome to the forum.

We could do it all in finance app, by pulling all extra payments into NPV

All we need is terms and rate, and the list of extra payments.
Example, loan is 5% APY, compounded monthly, terms is 30 years (N=360)

At N=2, extra payment of $1000
At N=20, extra payment of $2000

Finance app: I%YR=5, P/Yr=12, C/Yr=12, End=√, PMT=0

// shift N=20 payments to N=2
N=18, FV=2000 → PV=−1855.7761122

// shift N=2 payments to N=0, i.e. NPV
N=2, FV=1000-(−1855.7761122) → PV=−2832.12589423

// Spread NPV effect to regular payments
N=360, FV=0 → PMT=15.2034641912