Now that is a more useful reply than "Why do you assume there is one?". Thanks a lot Ravi!
--- On Fri, 9/17/10, Ravi Varadhan <rvarad...@jhmi.edu> wrote: From: Ravi Varadhan <rvarad...@jhmi.edu> Subject: RE: [R] Is there a bisection method in R? To: "'Peter Dalgaard'" <pda...@gmail.com>, "'Gregory Gentlemen'" <gregory_gentle...@yahoo.ca> Cc: r-help@r-project.org Received: Friday, September 17, 2010, 5:44 PM Here is something simple (does not have any checks for bad input), yet should be adequate: bisect <- function(fn, lower, upper, tol=1.e-07, ...) { f.lo <- fn(lower, ...) f.hi <- fn(upper, ...) feval <- 2 if (f.lo * f.hi > 0) stop("Root is not bracketed in the specified interval \n") chg <- upper - lower while (abs(chg) > tol) { x.new <- (lower + upper) / 2 f.new <- fn(x.new, ...) if (abs(f.new) <= tol) break if (f.lo * f.new < 0) upper <- x.new if (f.hi * f.new < 0) lower <- x.new chg <- upper - lower feval <- feval + 1 } list(x = x.new, value = f.new, fevals=feval) } # An example fn1 <- function(x, a) { exp(-x) - a*x } bisect(fn1, 0, 2, a=1) bisect(fn1, 0, 2, a=2) Ravi. -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Peter Dalgaard Sent: Friday, September 17, 2010 4:16 PM To: Gregory Gentlemen Cc: r-help@r-project.org Subject: Re: [R] Is there a bisection method in R? On 09/17/2010 09:28 PM, Gregory Gentlemen wrote: > If uniroot is not a bisection method, then what function in R does use bisection? > Why do you assume that there is one? uniroot contains a better algorithm for finding bracketed roots. It shouldn't be too hard to roll your own if you need one for pedagogical purposes. -- Peter Dalgaard Center for Statistics, Copenhagen Business School Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]]
______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.