Thanks for your fast advises. A simple examples of SEIR model is shown below:
#expample of very simple SEIR model##### library(odesolve) times<-seq(0,1200,1) parms<-c( b=0.35, #BETA OR COEFFICIENT OF TRANSMISSION pl=1/7, #LATENCY g=1/21, #RECOVERY a=0.05/7 #LETHALITY IN ADULT ) xstart<-c(S=100,E=0,I=1,R=0,nn=101) model<-function(t,x,parms){ S <-x[1] E <-x[2] I <-x[3] R <-x[4] nn <-x[5] with(as.list(parms),{ dS<--S*b*I/nn dE<-S*b*I/nn-E*pl dI<-E*pl-I*(a+g) dR<-I*g dnn<-dS+dE+dI+dR list(c(dS,dE,dI,dR,dnn)) }) } out<-as.data.frame(lsoda(xstart,times,model,parms)) plot(times,out$S,type="l") lines(times,out$E,col="green") lines(times,out$I,col="red") lines(times,out$R,col="blue") ######### I'd like to vary one or more parameters (with several distribution) for obtaining probabilistic results from the model projections. Now I'll try also with winBUGS, but I've never worked with it. I hope.. Thank you very much. Max On Thu, 16 Nov 2006 09:26:12 -0500 Tamas K Papp <[EMAIL PROTECTED]> wrote: > On Thu, Nov 16, 2006 at 02:55:07PM +0100, Massimo Fenati >wrote: >> Dear colleagues, >> Im a new R-help user. Ive read the advertisements >>about >> the good manners and I hope to propose a good question. >> Im using R to build an epidemiological SEIR model based >> on ODEs. The odesolve package is very useful to solve >> deterministic ODE systems but Id like to perform a >> stochastic simulation based on Markov chain Montecarlo >> methods. I dont know which packages could be used to do >> it (I tried with "sde" but without results). >> Have you some suggestions about useful methods and/or >> function in R for reaching my aim. > > Hi Max, > > I don't know what SEIR is. R has some MCMC packages > (RSiteSearch("MCMC") will help you there), but it is >easy to write a > Metropolis/Gibbs sampler yourself, making use of the >structure of your > problem. > > The sde package is for approximating likelihoods of >continuous time > stochastic differential equations (which is a difficult >problem by > itself). > > It is hard to give more advice without knowing what you >are trying to > achieve -- it is good that you have read the posting >guide, but please > give more details if you want more specific answers. > > HTH, > > Tamas MASSIMO FENATI ----------------------------------------- Istituto Nazionale per la Fauna Selvatica Via Cà Fornacetta, 9 40064 - Ozzano dell'Emilia (BO)- Italy tel: +39 0516512245 cel: +39 3392114911 fax: +39 051796628 e-mail: [EMAIL PROTECTED] ______________________________________________ R-help@stat.math.ethz.ch 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.