[R] Maximum likelihood estimate of bivariatevonmises-weibulldistribution

[Chaouch, Aziz]

Thanks Ravi! I'll contact you off the list as this is of high interest
to me. I'll also check that paper by Singh and Demchuk......if my more
than limited understanding of maths and statistics allows me to do so :)

Thanks also to Dimitris, I'll first try to get more info on the copula
package and then see how to choose the best copula model as you
suggested.

Aziz

-----Original Message-----
From: Ravi Varadhan [mailto:rvaradhan at jhmi.edu] 
Sent: May 12, 2006 1:41 PM
To: Chaouch, Aziz; 'Dimitris Rizopoulos'; hydinghua at gmail.com
Cc: r-help at stat.math.ethz.ch
Subject: RE: [R] Maximum likelihood estimate of
bivariatevonmises-weibulldistribution

Hi Aziz,

One of my friends recently wrote his PhD thesis from University of Leeds
under Kanti Mardia's direction.  He has dealt with different models for
bivariate von Mises distribution, and also with ML estimation for binary
mixtures of bivariate von Mises using EM algorithm, and also with Gibbs
Sampling for drawing from the posteriors.  If you are interested, you
can contact me off the list and I can put you in touch with him.

There is also a paper by Singh and Demchuk (Biometrika 2002) that is
highly relevant to your question.

Best,
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
------------------------------------------------------------------------
--

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch [mailto:r-help- 
> bounces at stat.math.ethz.ch] On Behalf Of Chaouch, Aziz
> Sent: Friday, May 12, 2006 9:13 AM
> To: Dimitris Rizopoulos; hydinghua at gmail.com
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] Maximum likelihood estimate of bivariatevonmises- 
> weibulldistribution
> 
> Thanks a lot! I wasn't aware of that copula package and it could well 
> be appropriate to use it for my application. However if I read the 
> copula help correctly, I still need to know what kind of copula to use

> to link the distribution of wind speeds and directions. Is there a way

> to determine this in R?
> 
> Moreover can I use the Von Mises distribution from the circular or 
> CircStats package into the mvdc function of the copula package or does

> the mvdc function only recognize distributions available "natively"
> within R?
> 
> Thanks again to all, your help is highly appreciated for a newbie like

> me!
> 
> Regards,
> 
> Aziz
> 
> -----Original Message-----
> From: Dimitris Rizopoulos [mailto:dimitris.rizopoulos at med.kuleuven.be]
> Sent: May 12, 2006 3:01 AM
> To: Philip He; Chaouch, Aziz
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] Maximum likelihood estimate of bivariate 
> vonmises-weibulldistribution
> 
> 
> ----- Original Message -----
> From: "Philip He" <hydinghua at gmail.com>
> To: "Chaouch, Aziz" <achaouch at nrcan.gc.ca>
> Cc: <r-help at stat.math.ethz.ch>
> Sent: Thursday, May 11, 2006 11:21 PM
> Subject: Re: [R] Maximum likelihood estimate of bivariate 
> vonmises-weibulldistribution
> 
> 
> > On 5/11/06, Chaouch, Aziz <achaouch at nrcan.gc.ca> wrote:
> >>
> >> Hi,
> >>
> >> I'm dealing with wind data and I'd like to model their distribution

> >> in order to simulate data to fill-in missing values. Wind direction

> >> are typically following a vonmises distribution and wind speeds 
> >> follow a weibull distribution. I'd like to build a joint 
> >> distribution
> 
> >> of directions and speeds as a VonMises-Weibull bivariate 
> >> distribution.
> >
> >
> > In order to built a bivariate distribution from two marginal 
> > distributions (wind direction, wind speed) , more information is 
> > needed to specify the relation between these two marginal 
> > distributions.For example, a conditional distribution may help.
> >
> 
> 
> An alternative in such cases (i.e., when marginals are available but 
> the joint is difficult to postulate) is to use copulas, which can 
> construct multivariate distributions from univariate marginals. If 
> this is appropriate for this application, the "copula" package might
be of help.
> 
> Best,
> Dimitris
> 
> ---
> Dimitris Rizopoulos
> Ph.D. Student
> Biostatistical Centre
> School of Public Health
> Catholic University of Leuven
> 
> Address: Kapucijnenvoer 35, Leuven, Belgium
> Tel: +32/(0)16/336899
> Fax: +32/(0)16/337015
> Web: http://www.med.kuleuven.be/biostat/
>      http://www.student.kuleuven.be/~m0390867/dimitris.htm
> 
> 
> Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
> 
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