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Examples of networks
Creating a simple network
The example
function is the typical example.
It is using the monad BNMonad
. The goal of this monad is to offer
a way of describing the network which is natural.
There are only three functions to understand inside the monad:

variable
to create a discrete variable of typeDV
. Creating a discrete variable is using aBounded
andEnum
type like for instanceBool
. 
proba
to define the probability P(A) of a variable A 
cpt
to define the conditional probability table P(A  BC)
It is important to understand how the values are organized. If you define P( wet  sprinkler road) then you have to give the values in the order:
wet=False, sprinkler=False, road=False wet=False, sprinkler=False, road=True wet=False, sprinkler=True, road=False wet=False, sprinkler=True, road=True
Finally, don't forget to return the discrete variables at the end of your network construction because those variables are used for making inferences.
example :: (DVSet
,SBN
CPT
) example =runBN
$ do winter <variable
"winter" (t :: Bool) sprinkler <variable
"sprinkler" (t :: Bool) wet <variable
"wet grass" (t :: Bool) rain <variable
"rain" (t :: Bool) road <variable
"slippery road" (t :: Bool) proba
winter ~~ [0.4,0.6]cpt
sprinkler [winter] ~~ [0.25,0.8,0.75,0.2]cpt
rain [winter] ~~ [0.9,0.2,0.1,0.8]cpt
wet [sprinkler,rain] ~~ [1,0.2,0.1,0.05,0,0.8,0.9,0.95]cpt
road [rain] ~~ [1,0.3,0,0.7] return [winter,sprinkler,rain,wet,road]
Importing a network from a Hugin file
The exampleImport
function can be used to import a file in Hugin format.
Only a subset of the format is supported.
The function will return a mapping from node names to Discrete Variables DV
.
The node name is used and not the node's label.
The function is also returning a simple bayesian network SBN
using CPT
as factors.
The implementation is using getDataFileName
to find the path of the
test pattern installed by cabal.
exampleImport :: IO (Map.Map StringDV
,SBN
CPT
) exampleImport = do path <getDataFileName
"cancer.net" r <importBayesianGraph
path return (runBN
$ fromJust r)
 example :: (DVSet, SBN CPT)
 exampleJunction :: UndirectedSG () Vertex
 exampleImport :: IO (Map String DV, SBN CPT)
 exampleDiabete :: IO (Map String DV, SBN CPT)
 exampleAsia :: IO (Map String DV, SBN CPT)
 examplePoker :: IO (Map String DV, SBN CPT)
 exampleFarm :: IO (Map String DV, SBN CPT)
 examplePerso :: IO (Map String DV, SBN CPT)
 testJunction :: DirectedSG () Vertex
 anyExample :: FilePath > IO (Map String DV, SBN CPT)