Re: Amortization Schedule--Global Symbol Value Error

*To*: mathgroup at smc.vnet.net*Subject*: [mg126591] Re: Amortization Schedule--Global Symbol Value Error*From*: djorser at comcast.net*Date*: Mon, 21 May 2012 05:59:40 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

Replace t=j/12; with t[j_]:=j/12; and replace references to t inside of Manipulate to t[j]. This will get you numeric values so you can correct your issue concerning incorrect values. Be sure to do Clear[t] if you have executed t=j/12; Don Orser ----- Original Message ----- From: "waterhand" <sandwaterhand at gmail.com> To: mathgroup at smc.vnet.net Sent: Sunday, May 20, 2012 2:36:13 AM Subject: [mg126591] Amortization Schedule--Global Symbol Value Error Let me begin by saying that I am very new to Mathematica, so any help is appreciated. I am trying to make an amortization schedule in a table format. The code I have is below: *** (* psv = Present Value, r = interest rate as a decimal, t = time in years, k = number of payments made *) (* mortgage function calculates the monthly mortgage amount *) mortgage[psv_, r_, t_] := N[psv*(r/12)/(1 - (1 + r/12)^(-12*t)), 2] (* amountLeftOwed function calculates the amount left on the loan including interest *) amountLeftOwed[psv_, r_, t_, k_] := N[psv*(1 + r/12)^k - mortgage[psv, r, t]*((1 + r/12)^k - 1)/(r/12), 2] (* paidInInterest function calculates the amount of the mortgage payment that goes towards the interest *) paidInInterest[psv_, r_, t_, k_] := N[amountLeftOwed[psv, r, t, k]*r/12, 2] (* paidInPrincipal function calculates the amount of the mortgage payment that goes towards the principal *) paidInPrincipal[psv_, r_, t_, k_] := N[mortgage[psv, r, t] - paidInInterest[psv, r, t, k], 2] (* remainingBalance function gives the remaining balance after payment has been made *) remainingBalance[psv_, r_, t_, k_] := N[amountLeftOwed[psv, r, t, k] - mortgage[psv, r, t], 2] (* j is the number of months. this converts months to years *) t = j/12; Manipulate[ TableForm[ Prepend[ Table[{i, paidInInterest[psv, r, t, i], paidInPrincipal[psv, r, t, i], remainingBalance[psv, r, t, i]}, {i, 1, j}], {"Month", "Interest", "Principal", "Balance"}]], {{psv, 100000, "Loan Amount"}, 100, 200000, 100}, {{r, 0.05, "Interest Rate"}, 0.01, .1, 0.0005}, {{j, 120, "Number of Months"}, {120, 240, 360}} ] *** Here's the issues I am having: 1) The variable j is coming up with the "Global symbols that have no assigned value" error despite it being assigned 120, 240, and 360 in the Manipulate[] function. When I add a line like "j = 120", the code "works". The reason for the quotations is explained in number 3 below. 2) Despite the N[*, 2] function, the numbers are coming out as scientific notation. Even with the line j = 120, the rounding is not to two places. 3) The table should end with the ending balance being zero. When I force the value of j (again, j = 120, 240, or 360), I am getting a negative value for the last two months. Is there a rounding issue related to #2? Again, very new to Mathematica. I appreciate any help. Thanks for reading, Mike