From: Sungsu <skim033_at_ucr.edu>

Date: Mon, 14 Apr 2008 05:53:36 -0700 (PDT)

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. Received on Mon 14 Apr 2008 - 13:22:34 GMT

Date: Mon, 14 Apr 2008 05:53:36 -0700 (PDT)

Dear Spencer.

Thank you for your kind reply.

I have n data points observed on the surface of a torus. I am trying to fit the geodesic line equation to these points on the surface:

the equation is

‘u=h*integrate(((5+cos(v))*sqrt((5+cos(v))^2-h^2))^{-1})
from 0 to v’.

I wrote the following R code to make the above function.

fun<-function(h)

{

u<-h*integrate(((5+cos(y))*sqrt((5+cos(y))^2-h^2))^(-1)),lower=0,upper=v)$value

u

}

Then minimized the sum of

(1-cos(u-h**integrate(((5+cos(y))*sqrt((5+cos(y))^2-h^2))^(-1)),lower=0,upper=v)$value)
as:

nlminb(c(1),fun,lower=0,upper=9)

I did not get an error, but the estimated h is 9 or 0, these are just boundaty values.

I would like to appreciate your help.

Sungsu

**UCR
**
ps: you may use any sized two vectors for u and v
with values from 0 to 2pi in the above equation.

- Original message ----

Date: Sun, 13 Apr 2008 13:54:17 -0700

From: Spencer Graves <spencer.graves_at_pdf.com>
Subject: Re: [R] nonlinear curve fitting on a
torus

To: Sungsu <skim033_at_ucr.edu>

Cc: r-help_at_r-project.org

> Having seen no reply to this, I will offer a

couple of comments

>that may or may not be useful. Googling for

"geodesic equation on a

>torus" produced interesting hits, but

RSiteSearch("geodesic equation on

>a torus") found nothing. RSiteSearch("torus")

returned 33 hits, some of

>which referred to a package "geozoo".

* >
** > If you want a solution of a differential
*

equation, you might

>consider lsoda {odesolve}. The 'fda' package may

also be useful.

* >
*

> To say more, I'd prefer to hear more specifics

from you. PLEASE

>do read the posting guide

"http://www.R-project.org/posting-guide.html"

>and provide commented, minimal, self-contained,

reproducible code.

>Doing so can make it much easier for people to

understand what you

>want. If you provide code that doesn't quite

work, someone who is

>interested can copy it from your email into R and

try things, possibly

>generating a solution to your problem. Without a

self-contained

>example, you restrict the pool of possible

respondents to people who

>have actually worked with a "geodesic equation on

a torus" -- or to

>fools like me who are willing to expose their

ignorance commenting on

>something we know essentially nothing about.

* >
** > Hope this helps.
** > Spencer Graves
** >
** >Sungsu wrote:
** >> Dear R users.
** >>
** >> I have data observed on the surface of a torus,
*

and

>> am trying to fit the nonlinear regression using

* >>
** >> the geodesic equation on a torus. Could anyone
*

give

>> me a helpful advise on this problem? I would

* >> definitely appreicate your reply.
** >>
** >> Sincerely,
** >>
** >> SUNGSU KIM
** >>
** >> [[alternative HTML version deleted]]
** >>
** >> ______________________________________________
** >> 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.

* >>
*

[[alternative HTML version deleted]]

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. Received on Mon 14 Apr 2008 - 13:22:34 GMT

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