# User-defined monthly loan payment function issues

16 vues (au cours des 30 derniers jours)
Sydney le 12 Mai 2024
Commenté : Sydney le 12 Mai 2024
Hello! I am trying to create a very simple user-defined function to calculate monthly payments on a loan, but I am unsure why my function is returning "0". I am sure it must be a silly formatting error, but I would appreciate any help pointing out my mistake! Thank you!
% amort returns monthly payment of a loan given the loan amount, annual interest
% rate, and length of loan
% P=loan amount
% r=annual interest rate (in percent)
% N=length of loan in years
function [M]=amort(P,r,N)
M=P*((r/1200)/(1-(1+(r/1200)))^((-12)*N))
##### 2 commentairesAfficher AucuneMasquer Aucune
Walter Roberson le 12 Mai 2024
What are some example parameters to the call?
Sydney le 12 Mai 2024
One example I ran used P=260000, r=6.75, N=15
Is this what you were asking by parameters?
I called it using:
amort(260000,6.75,15)

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### Réponse acceptée

Walter Roberson le 12 Mai 2024
M=P*((r/1200)/(1-(1+(r/1200)))^((-12)*N))
12 1 2 3 4 321 23 2 10
That has a sub-expression (1-(1+(r/1200))) . That sub-expression simplifies to -(r/1200) . So you effectively have
P * ( (r/1200)/(-r/1200)^(-12*N) )
which is
P * (-r/1200)^(12*N + 1)
(or something similar)
It seems unlikely that is what you wanted.
##### 3 commentairesAfficher 1 commentaire plus ancienMasquer 1 commentaire plus ancien
Walter Roberson le 12 Mai 2024
You entered it wrong in MATLAB.
M = P * (r/1200) ./ (1 - (1+r/1200).^(-12*N))
Sydney le 12 Mai 2024

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