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From |
Lance Erickson <lance_erickson@byu.edu> |

To |
"statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: Calculating compound interest using loops? |

Date |
Mon, 9 Jul 2012 21:42:44 +0000 |

Hi Sara, Something like this (below) should give you a more efficient version of the code you had. Best, Lance // create test data clear input id principal rate payment 1 200000 .005 1199.1 end // get amount of monthly interest local interest = 0 forvalues i = 1/360 { local j = `i' - 1 gen int`i' = (principal - (payment*`j') + `interest') * rate local interest "`interest' + int`i'" } // get amount of yearly interest local l = 1 foreach k of numlist 12(12)360 { local m = `k' - 11 egen int_y`l' = rowtotal(int`m'-int`k') local ++l } -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Sara Kimberlin Sent: Monday, July 09, 2012 1:23 PM To: statalist@hsphsun2.harvard.edu Subject: st: Calculating compound interest using loops? Hello, I'm trying to calculate annual interest payments on a 30-year loan, with interest compounding monthly, and can't figure out how to write the code efficiently. Pre-defined variables include principal, rate, and monthly_payment. I know I can manually calculate the amount of interest for each monthly period like this: gen interest_month1 = principal * rate gen interest_month2 = (principal - (monthly_payment * 1) + interest_month1) * rate gen interest_month3 = (principal - (monthly_payment * 2) + interest_month1 + interest_month2) * rate gen interest_month4 = (principal - (monthly_payment * 3) + interest_month1 + interest_month2 + interest_month3) * rate ... and so on through interest_month360. And then I can manually add up the monthly interest to calculate the annual interest for each year, e.g.: gen interest_year1 = interest_month1 + interest_month2... + interest_month12 But I think there must be a way to write this much more efficiently using loops, and I haven't been able to figure it out. I'd appreciate any help. Thank you, Sara * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: RE: Calculating compound interest using loops?***From:*Karen Zhang <mathkaren@me.com>

**Re: st: RE: Calculating compound interest using loops?***From:*Sara Kimberlin <skimberlin@gmail.com>

**References**:**st: Calculating compound interest using loops?***From:*Sara Kimberlin <skimberlin@gmail.com>

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