Set, update and remove evidence.

evidence_add(object, evidence, propagate = TRUE, details = 0)

evidence_get(object, short = TRUE)

evidence_drop(object, nodes = NULL, propagate = TRUE)

evidence_prob(object, evidence = NULL)

Arguments

object: A "grain" object
evidence: A list of name=value. See examples below.
propagate: Should the network be propagated?
details: Debugging information
short: If TRUE a dataframe with a summary is returned; otherwise a list with all details.
nodes: A vector of nodes.

Value

A list of tables with potentials.

Note

setEvidence() is an improvement of setFinding() (and as such setFinding is obsolete). Users are recommended to use setEvidence() in the future.

setEvidence() allows to specification of "hard evidence" (specific values for variables) and likelihood evidence (also known as virtual evidence) for variables.

The syntax of setEvidence() may change in the future.

References

Søren Højsgaard (2012). Graphical Independence Networks with the gRain Package for R. Journal of Statistical Software, 46(10), 1-26. https://www.jstatsoft.org/v46/i10/.

Author

Søren Højsgaard, sorenh@math.aau.dk

Examples


example("example_chest_cpt")
#> 
#> exmp__> yn   <- c("yes", "no")
#> 
#> exmp__> a    <- cpt(~asia, values=c(1,99),levels=yn)
#> 
#> exmp__> t.a  <- cpt(~tub|asia, values=c(5,95,1,99),levels=yn)
#> 
#> exmp__> s    <- cpt(~smoke, values=c(5,5), levels=yn)
#> 
#> exmp__> l.s  <- cpt(~lung|smoke, values=c(1,9,1,99), levels=yn)
#> 
#> exmp__> b.s  <- cpt(~bronc|smoke, values=c(6,4,3,7), levels=yn)
#> 
#> exmp__> e.lt <- cpt(~either|lung:tub,values=c(1,0,1,0,1,0,0,1),levels=yn)
#> 
#> exmp__> x.e  <- cpt(~xray|either, values=c(98,2,5,95), levels=yn)
#> 
#> exmp__> d.be <- cpt(~dysp|bronc:either, values=c(9,1,7,3,8,2,1,9), levels=yn)
#> 
#> exmp__> chest_cpt <- list(a, t.a, s, l.s, b.s, e.lt, x.e, d.be)
#> 
#> exmp__> ## bn <- grain(compile_cpt(chest_cpt))
#> exmp__> 
#> exmp__> 
#> exmp__> 
chest.bn <- grain(compileCPT(chest_cpt))

bn2 <- chest.bn |> evidence_add(list(asia="yes", xray="yes"))
bn3 <- chest.bn |> evidence_add(list(asia=c(0.8, 0.1), xray="yes"))

bn2 |> evidence_get()
#>   nodes is_hard hard_state evi_weight
#> 1  asia    TRUE        yes       1, 0
#> 2  xray    TRUE        yes       1, 0
bn3 |> evidence_get()
#>   nodes is_hard hard_state evi_weight
#> 1  asia   FALSE       <NA>   0.8, 0.1
#> 2  xray    TRUE        yes       1, 0

bn2 |> evidence_prob()
#> [1] 0.001450925
bn3 |> evidence_prob()
#> [1] 0.01204465

bn2 |> evidence_drop("xray")
#> Independence network: Compiled: TRUE Propagated: TRUE Evidence: TRUE 
bn3 |> evidence_drop("xray")
#> Independence network: Compiled: TRUE Propagated: TRUE Evidence: TRUE 

bn2 |> evidence_drop("xray") |> evidence_get()
#>   nodes is_hard hard_state evi_weight
#> 1  asia    TRUE        yes       1, 0
#> 2  xray    TRUE        yes       1, 0
bn3 |> evidence_drop("xray") |> evidence_get()
#>   nodes is_hard hard_state evi_weight
#> 1  asia   FALSE       <NA>   0.8, 0.1
#> 2  xray    TRUE        yes       1, 0

## For backward compatibility these functions are available now but
#may be deprecated later.
bb2 <- setEvidence(chest.bn, c("asia", "xray"), c("yes", "yes"))
bb3 <- setEvidence(chest.bn, c("asia", "xray"), list(c(0.8, 0.2), "yes"))
bb4 <- setFinding(chest.bn, c("asia", "xray"), c("yes", "yes"))

bb2 |> getEvidence()
#>   nodes is_hard hard_state evi_weight
#> 1  asia    TRUE        yes       1, 0
#> 2  xray    TRUE        yes       1, 0
bb3 |> getEvidence()
#>   nodes is_hard hard_state evi_weight
#> 1  asia   FALSE       <NA>   0.8, 0.2
#> 2  xray    TRUE        yes       1, 0

bb2 |> retractEvidence("xray")
#> Independence network: Compiled: TRUE Propagated: TRUE Evidence: TRUE 
bb3 |> retractEvidence("xray")
#> Independence network: Compiled: TRUE Propagated: TRUE Evidence: TRUE 

bb2 |> pEvidence()
#> [1] 0.001450925
bb3 |> pEvidence()
#> [1] 0.02292856

bb2 |> retractEvidence("xray") |> getEvidence()
#>   nodes is_hard hard_state evi_weight
#> 1  asia    TRUE        yes       1, 0
#> 2  xray    TRUE        yes       1, 0
bb3 |> retractEvidence("xray") |> getEvidence()
#>   nodes is_hard hard_state evi_weight
#> 1  asia   FALSE       <NA>   0.8, 0.2
#> 2  xray    TRUE        yes       1, 0