[R] calculating IRR (accounting) in R

[McGehee, Robert]

Hello,
If we define IRR implicitly such that NPV(C, IRR) = 0, then we can just
write an IRR function that finds the zeros of the NPV function. Here are
two such functions:

NPV <- function(C, r) {
    sum(C / (1 + r) ^ (seq(along = C) - 1))
}

IRR <- function(C) {
    uniroot(NPV, c(0, 1), C = C)$root
}

Hope this helps,
Robert

-----Original Message-----
From: paul sorenson [mailto:sourceforge at metrak.com] 
Sent: Wednesday, November 30, 2005 3:50 PM
To: r-help
Subject: [R] calculating IRR (accounting) in R


I am trying to replace a spreadsheet model of a project justification 
with an R script.

I can't seem to track down R functions to calculate Internal Rate of 
Return and NPV?  Am I missing something?  NPV doesn't seem so difficult 
to calculate (at least for a regular series) but I am struggling to 
identify how to solve for IRR in R.

It would be sufficient if it worked for a regular series but really 
useful if there was something that worked with irregular time series.

cheers

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