(12C) Error Function Approximation
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10-02-2019, 03:21 AM
(This post was last modified: 10-02-2019 03:25 AM by Eddie W. Shore.)
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(12C) Error Function Approximation
The program for the HP 12C calculator approximates the error function defined as
erf(x) = 2 / √π * ∫ e^-(t^2) dt from t = 0 to t = x by using the series erf(x) = (2*x) / √π * Σ( (-x^2)^n / (n!*(2*n+1)), n = 0 to ∞) In the approximation, up to 69 terms are calculated for the sum (the loop stops when n = 69). Since there is no π constant on the HP 12C, the approximation 355/113 for π is used. Program: Code: Step; Key Code; Key Examples (FIX 5) erf(0.5) ≈ 0.52050 erf(1.6) ≈ 0.97635 erf(2.3) ≈ 0.99886 Source Ball, John A. Algorithms for PRN Calculators John Wiley & Sons: New York 1978 ISBN (10) 0-471-0370-8 |
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(12C) Error Function Approximation - Eddie W. Shore - 10-02-2019 03:21 AM
RE: (12C) Error Function Approximation - Albert Chan - 10-05-2019, 12:26 PM
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