A formula for IRR

[salvomic]

hi,
you can find in the HP Prime Software Library a much better version of the program, or ...two version: the first with the single functions exported (the user can recall them separately), the second with Drawmenu (every functions inside, but with a graphic interface).

I had to use a trick to avoid a strange erratic first argument output by solve() with the function for IRR, with a IRR value greater than 1 (100%) in some cases but not all...

Code:


irr:= solve(ΣLIST(MAKELIST((L1(I)/X^(I-1)),I,1,SIZE(L1))),X)-1;
IF (irr(1)>=1 OR irr(1)<=-1) THEN irr:=tail(irr); END;
// formula by akmon, Cyrille, Dale

please, control with examples, if possibles...

Enjoy!

Salvo