41C/CV root finders
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05-26-2015, 05:39 PM
(This post was last modified: 05-26-2015 05:40 PM by Dieter.)
Post: #18
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RE: 41C/CV root finders
(05-26-2015 05:06 AM)Ángel Martin Wrote: The exponent signs were not handled well in the copy-paste action; I have corrected the expressions in the initial post now. OK. But back to the initial guess: does it really evaluate to 165% for the sample case, or did I understand something wrong? (05-26-2015 05:06 AM)Ángel Martin Wrote: I fail to see how reducing the initial guess to a near-zero value will solve the problem when there is not a solution to be found...which is the only problem left. No, of course an estimate close to zero will not solve cases where no (real) solution exists. But it saves memory space at the cost of merely one more iteration. (05-26-2015 05:06 AM)Ángel Martin Wrote: Again, the initial guess I use works rather well for all other *solvable* cases, it's sweet and short to obtain and doesn't require too many iterations to converge. Please forgive me if I get back to this point once again, but I simply want to know: How many iterations are required for the example posted in this thread until the result (14,436%) is returned? Does the algorithm actually return the lower one of the two solutions (the other one being 53,172%), although the first estimate is as high as 165%? Since |PV+n*PMT+FV| usually is > 1, the estimate will (almost) always be > 100%. And finally... may I ask this...? Would you mind trying your algorithm with a first estimate of 1E–4? How does it behave? Dieter |
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