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:[EMAIL PROTECTED] 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 ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html