[SYNTAX] Density Function in deterministic definition

[bhlbarxios]

density distribution functions (dnorm, dunif, dbeta) can't be used in deterministic definitions ( <- )
model{
ab <- dnorm(1,1)
}
dnorm should be detected as an error

[opcoach]

Could you please enumerate exactly the distribution functions ?

They will not be proposed in auto completion after the '<-'

Only dnorm, dunif and dbeta or are there some others from this list : (dlnorm for instance ? )

dbern, dbeta , dbin , dchisqr, ddexp, dexp, df, dgamma, dgengamm, dhyper, dlogis, dlnorm, dnegbin, dnchisqr, dpar, dpois, dt, dweib

[opcoach]

In the first documentation example for instance dgamma is used for the tau ~ :

model {
for (i in 1:N) {
Y[i] ~ dnorm(mu[i], tau)
mu[i] <- alpha + beta * (x[i] - x.bar)
}
x.bar <- mean(x)
alpha ~ dnorm(0.0, 1.0E-4)
beta ~ dnorm(0.0, 1.0E-4)
sigma<- 1.0/sqrt(tau)
tau ~ dgamma(1.0E-3, 1.0E-3)
}

[opcoach]

Benoit,
Could you check what are the distribution functions ? The list is available in the xtext grammar file here :

https://github.com/opcoach/jagsy/blob/master/bugsy/com.opcoach.bugsy.xtext/src/com/opcoach/bugsy/xtext/BugsDsl.xtext

[bhlbarxios]

I looked to the lists in the xtext file:
enum DistributionOperator:
dbern='dbern' | dbin='dbin' | dchisqr='dchisqr' | ddexp='ddexp' | dexp='dexp' | df='df' |
dgengamm='dgen.gamma' | dhyper='dhyper' | dlogis='dlogis' | dlnorm='dlnorm' | dnegbin='dnegbin' | dnchisqr='dnchisqr'
| dpar='dpar' | dpois='dpois' | dt='dt';

enum DensityOperator:
dnorm='dnorm' | dunif='dunif' | dbeta='dbeta' | dgamma='dgamma' | dweib = 'dweib' | weibul = 'weibul' ;

I don't understand why there are two lists for these operators. There are characterizing random nodes by using Probability Distributions. There are all part of the same family of mathematical objects. I don't see the multivariate distributions (multinormal, wishart, etc) in the list. That's strange to have both "dweib" and "weibul". Why did you include weibul into the list?

[opcoach]

The title of the bug is : density distributions can't be used in deterministic definitions (<-)

Therefore, it is necessary to separate what is available for <- and ~ definitions (dnorm can only be in ~), so there are 2 enums for this.

The content of these enums has probably to be fixed.

I added 'weibul' when I fixed the issue#22, but I didn't understand it is the name for dweib :-) I will change it.

[bhlbarxios]

In fact, in "<-" only what you have defined as FunctionOperators can be used - In other words, never what you defined as DistributionOperators and DensityOperators. These two last types of operators represent the same type of mathematical objects.

The main point is that in a "~" relation you can have both Distribution/DensityOperators and FunctionOperators (the second type used for characterizing the parameters of the first type).

e.g.: X ~ dnorm( a+exp(b) ,sigma ) with dnorm distribution/densityoperators and exp functionoperators
It is always possible to define a dummy variable in order to avoid such combination, e.g.
X ~ dnorm(mu,sigma)
mu <- a + exp(b)