On 5/11/06, Chaouch, Aziz <[EMAIL PROTECTED]> 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. First is this a stupid question? I'm a newbie in statistics and R :) > > Is it possible to do it in R? > > Is there a way to estimate the parameters of the bivariate distribution > using maximum likelihood? Do you have some hints on how to do this in R > (with optim for example)? > > The second problem is that the distribution of wind direction is > sometime bimodal (likely to be due to topography). Is it possible to > model the distribution as a mixture of 2 von mises distribution and > build a awfully complex joint distribution that would be "mixture of 2 > von mises - weibull"???? Yes, you can model wind direction as a mixture of two von miese distributions, but be aware of the computation burden. In R, optim() is a good condidate function for maximization if the number of parameters are not large. Thanks a lot, > > Aziz > > > > [[alternative HTML version deleted]] > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > [[alternative HTML version deleted]] ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
