> > >From: robert-mcfadden w o2.pl > > >Date: 2008/04/02 Wed AM 09:58:28 CDT > > >To: r-help w r-project.org > > >Subject: [R] Nonlinear equation > > > > hi: you need to give an example and details or > > you won't get much response, if any.Equation e.g. (A, B are known constants): 3log(gamma(x))-log(gamma(x)*gamma(2x))+(x-1)*A+B=0
Here is an approach using optim().
fn <- function(x, A, B) {
(2*lgamma(x) + lgamma(2*x)+ (x-1)*A + B)^2
}
ans <- optim(par=1, fn, A=1.5, B=1.0, method="BFGS")
You should plug in your values for A and B. Make sure that the function
value returned ny optim, i.e. ans$val, is close to zero. If not, try a
different starting value.
Ravi.
----------------------------------------------------------------------------
-------
Ravi Varadhan, Ph.D.
Assistant Professor, The Center on Aging and Health
Division of Geriatric Medicine and Gerontology
Johns Hopkins University
Ph: (410) 502-2619
Fax: (410) 614-9625
Email: rvaradhan at jhmi.edu
Webpage: http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html
----------------------------------------------------------------------------
--------
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of robert-mcfadden at o2.pl
Sent: Wednesday, April 02, 2008 11:25 AM
To: r-help at r-project.org
Subject: [R] Fwd: Re: Nonlinear equation
> > >From: robert-mcfadden at o2.pl
> > >Date: 2008/04/02 Wed AM 09:58:28 CDT
> > >To: r-help at r-project.org
> > >Subject: [R] Nonlinear equation
> >
> > hi: you need to give an example and details or
> > you won't get much response, if any.
Equation e.g. (A, B are known constants):
3log(gamma(x))-log(gamma(x)*gamma(2x))+(x-1)*A+B=0
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and provide commented, minimal, self-contained, reproducible code.
On 4/2/2008 11:24 AM, robert-mcfadden at o2.pl wrote:>> > >From: robert-mcfadden at o2.pl >> > >Date: 2008/04/02 Wed AM 09:58:28 CDT >> > >To: r-help at r-project.org >> > >Subject: [R] Nonlinear equation >> > >> > hi: you need to give an example and details or >> > you won't get much response, if any. > > Equation e.g. (A, B are known constants): > 3log(gamma(x))-log(gamma(x)*gamma(2x))+(x-1)*A+B=0uniroot() can solve that if you can bracket the solution. Duncan Murdoch
Also, note that depending on A and B there are likely to be multiple (or no) solutions to your equation. ---------------------------------------------------------------------------- ------- Ravi Varadhan, Ph.D. Assistant Professor, The Center on Aging and Health Division of Geriatric Medicine and Gerontology Johns Hopkins University Ph: (410) 502-2619 Fax: (410) 614-9625 Email: rvaradhan at jhmi.edu Webpage: http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html ---------------------------------------------------------------------------- -------- -----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of robert-mcfadden at o2.pl Sent: Wednesday, April 02, 2008 11:25 AM To: r-help at r-project.org Subject: [R] Fwd: Re: Nonlinear equation> > >From: robert-mcfadden at o2.pl > > >Date: 2008/04/02 Wed AM 09:58:28 CDT > > >To: r-help at r-project.org > > >Subject: [R] Nonlinear equation > > > > hi: you need to give an example and details or > > you won't get much response, if any.Equation e.g. (A, B are known constants): 3log(gamma(x))-log(gamma(x)*gamma(2x))+(x-1)*A+B=0 ______________________________________________ R-help at 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.