A formula for IRR

[salvomic]

(05-18-2015 09:20 AM)akmon Wrote:  Well it worked well for me in home mode Textbook format. Thank you Cyrille for the expression. Anyway I made two little changes:

fsolve(ΣLIST(MAKELIST((L1(I)/X^(I-1)),I,1,SIZE(L1))),X)-1

Example: L1= {-123400, 36200, 54800, 48100}

TIR = 0,0596, or 5,96%

(In spanish we call TIR -tasa interna de retorno- to IRR)

Very useful for me, cause I work with financial analysis in public works concessions.

I tried your example, Salvomic, and it nails it: 0,1306 or 13,06%.

good for you, akmon!
HP 12C confirms your example: IRR (TIR) = 5.96%

But I get warning: "evaluating invariable expression(value) like if expression was a function. You should write subst(48100/X^-1,X,0)"
then -1

I'm searching where is my error...

EDIT: I was in CAS...
In Home it works well!

So, now we must find a way to be able to use it also in CAS...
Then Eddie could add this to his nice program for NPV.

However I'm trying to port formula in an independent program IRR(lista), but it gives for now "Bad argument type" in Home, and a lot of warnings in CAS. Working in progress...

Salvo