41C/CV root finders

[Ángel Martin]

(05-27-2015 01:50 PM)Dieter Wrote:  You said the inital guess was evaluated as abs(PV+n*PMT+FV))^(1/n). Which is almost always > 1 i.e. > 100%. For the example the result is 150^0,1 = 1,650475 = 165,0475%. Hmmm... the actual estimate is exactly 1/100 of this, so your i0 formula must be slightly different.

correct - it is divided by 100 ;-)

(05-27-2015 01:50 PM)Dieter Wrote:  Hmm... 7 or 13 iterations? I am sure it works for you, but maybe... maybe I can trigger your ambition a bit anyway...? ;-) I tried a simple program in HP41 user code. It returns the two interest rates in both cases (begin and end mode) after merely 4 iterations. And both results are dead on.

I also tried the same algorithm with your initial estimate. Again, it took not more than 5 iterations, and both results were exact.

We're comparing apples to oranges - the number of MCODE loops are not exactly the same concepts as the iterations in the FOCAL code, sorry but that's not a one-to-one match. Besides the MCODE speed is significantly faster... are you saying that your FOCAL program finds the solution *faster* than the 12C?

(05-27-2015 01:50 PM)Dieter Wrote:  Please don't get me wrong. Everything is fine if the current implementation works for you. But I can't help: my ambition is to trigger yours. ;-)

And you have achieved that, so which initial guess do you suggest I should try?

Cheers,
ÁM