Hello WinBUGS users. I am hoping to use WinBUGS for my model. I have done the modelling, but I am a bit suspicious about the output. Hence it'll be of great help if someone can please point out if my WinBUGS code is correct wrt to the theoretical model. Model: w[j] ~ Mixture of exponential distributions with parameters lambda[1] and lambda[2] and P decides the probability of w[j] being generated from either of the exponential distributions. Some of the w[j] values are censored due to which I have to use dweib(1, mu[j]) instead of a simple exponential distribution. From the tutorial it seemed to me that the Weibull distribution supports censoring. Now some of the w[j]'s are generated from a single exponential distribution instead of the mixture. My confusion is regarding the WinBUGS code that handles this. I am doing it in the following manner. The first observation is generated from the mixture. Now w[j] is generated from only a single exponential distribution under the following conditions: For every w[j], there is a corresponding cen[j] which equals to 0 and cen[j-1] does not equal to 0. Also I have the variable M[j] that decides which of the exponential distribution generates the data. I use it as: Mod[j] <- equals(cen[j], 0)*(1 - equals(cen[j-1], 0)) + (1 - equals(cen[j], 0)*(1 - equals(cen[j-1], 0)) )*M[j] The first part is 1 if both the conditions are fulfilled and Mod[j] is assigned the value 1, otherwise the values is assigned based on M[j]. The complete WinBUGS model is as follows: model { for (j in 1 : 1) { w[j] ~ dweib(1, mu[j]) I(cen[j], ) mu[j] <- lambda[M[j]] M[j] ~ dcat(P[]) } for (j in 2 : T) { w[j] ~ dweib(1, mu[j]) I(cen[j], ) mu[j] <- lambda[Mod[j]] Mod[j] <- equals(cen[j], 0)*(1 - equals(cen[j-1], 0)) + (1 - equals(cen[j], 0)*(1 - equals(cen[j-1], 0)) )*M[j] M[j] ~ dcat(P[]) } P[1:2] ~ ddirch(alpha[]); alpha[1] <- 1; alpha[2] <- 1; lambda[1] ~ dnorm(0.0, 1.0E-6) I(0, ) l2 <- 1 - lambda[1] theta ~ dnorm(0.0, 1.0E-6) I(0, l2) lambda[2] <- lambda[1] + theta } Kindly suggest if I am making any errors in handling the mixture model especially assigning some of the observations that are generated from only a single distribution instead of the mixture. Thanks Avik ========== Avik Sarkar PhD Student Department of Computing Open University ; Milton Keynes ; UK homepage : http://mcs.open.ac.uk/as5297 http://www.aviksarkar.com ------------------------------------------------------------------- This list is for discussion of modelling issues and the BUGS software. For help with crashes and error messages, first mail [log in to unmask] To mail the BUGS list, mail to [log in to unmask] Before mailing, please check the archive at www.jiscmail.ac.uk/lists/bugs.html Please do not mail attachments to the list. To leave the BUGS list, send LEAVE BUGS to [log in to unmask] If this fails, mail [log in to unmask], NOT the whole list