Nonlinear equation

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

______________________________________________
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.
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
uniroot() 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.
On 4/2/2008 11:24 AM, robert-mcfadden w o2.pl wrote:
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
uniroot() can solve that if you can bracket the solution.

Duncan Murdoch
Thank you very much - that's exactly what I need.
 > >> > 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
 >
 > uniroot() can solve that if you can bracket the solution.
 Thank you very much - that's exactly what I need.
To bracket the solution, plot the curve of your function (?curve).

Paul