Complex math problem, how to write it in php

[radar]

This is about the worst math i've ever seen... i HATE math....  any help is appreciated...  The mathematical equation as based on actual math is:

 

n = -log(1-[Pi/(Mq)])/(q log[1+(i/q)])

 

where P = primary_loan ammount, i = interest rate, M = monthly payment and q = presumed # of payments per year (12 all the time)  so in my 'sample' it would be something like

 

P = 100,000, i= .1, M = 1400 and q = 12...  if the math comes out right it should come up with 9.08 or 9.1 if you round (which i dont want to do)

 

no clue how to do this in PHP.. any help appreciated... thanks..

[xyph]

Pretty straightforward

 

<?php 

$primary_loan = 100000;
$interest = 0.1;
$monthly = 1400;
$pay_per_year = 12;

$total = log( 1-(($primary_loan*$interest)/($monthly*$pay_per_year)) ) / 
( $pay_per_year*log(1+($interest/$pay_per_year)) ) * -1;

echo $total; // 9.0821962960889

/*
n = -log(1-[Pi/(Mq)])/(q log[1+(i/q)])

where P = primary_loan ammount, i = interest rate, M = monthly payment
and q = presumed # of payments per year (12 all the time)  so in my
'sample' it would be something like

P = 100,000, i= .1, M = 1400 and q = 12...  if the math comes out right
it should come up with 9.08 or 9.1 if you round (which i dont want to do)
*/

?>

[PFMaBiSmAd]

<?php

$P = 100000;
$M = 1400;
$q = 12;
$i = .1;

$n = -log(1-($P * $i/($M * $q)))/($q * log(1+($i/$q)));

echo $n;

?>

 

9.0821962960889

[radar]

man you guys are awesome....  In my years of programming php I've never had to do this type of math before so figuring out how to write it (being that i suck at math - almost 30 and can barely add and subtract really) was going to be a pain in the butt.....  thank you guys very much for helping me out I really appreciate it!

[radar]

Ahh just thought of something else, because the end-user will be able to input their interest rate at 10, 29.5 or any number inbetween 0 and 100%..  how would i use php to modify that into a decimal for use with this equation

[xyph]

Divide by 100

 

$number = 50;

$percent = $number / 100;

[radar]

beautiful.  thanks xyph...  saves me a ton of hassle within the next day or two...  I really appreciate it.