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Distrib()
specification
This specification indicates which variable to sample, and its sampling
distribution. One Distrib() specification must be included for
each variable to sample. The specification file can include any number
of these commands at the global level, or within any Level
section in the case of Markov chain Monte Carlo sampling
(see section 6.5 Specifying a statistical model). The syntax is:
Distrib(<identifier>, <iType>, [<shape parms>]); |
The iType field specifies the sampling distribution to use and can be one of following:
The corresponding shape parameters (Bernardo and Smith, 1994; Gelman et al., 1995) (see section Bibliographic References) are as follow:
Normal_v
takes the
variance instead of the standard deviation as second parameter.
TruncNormal_v
takes the variance instead of the standard
deviation as second parameter.
LogNormal_v
takes the variance (in log-space!) instead of
the standard deviation as second parameter.
Distrib(Var, TruncLogNormal, 1, 2.718, 0.01, 10) |
samples Var such that
log(Var) is a standardized normal variate - of mean log(1)Ê=Ê0
and standard deviation log(2.718)Ê=Ê1 -
while Var is truncated to fall between 0.01 to 10. The variant
TruncLogNormal_v
takes the variance (in log-space!) instead of
the standard deviation as second parameter.
The shape parameters of the above distribution specifications can reference other parameters, provided than distributions for these have already been defined. For example:
Distrib(A, Normal, 0, 1); Distrib(B, Normal, A, 2); |
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