R Under development (unstable) (2024-02-05 r85863 ucrt) -- "Unsuffered Consequences"
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> library(pcalg)
> 
> # Y-structure MAG
> # Encode as adjacency matrix
> p <- 4 # total number of variables
> V <- c("X1","X2","X3","X4") # variable labels
> # amat[i,j] = 0 iff no edge btw i,j
> # amat[i,j] = 1 iff i *-o j
> # amat[i,j] = 2 iff i *-> j
> # amat[i,j] = 3 iff i *-- j
> amat <- rbind(c(0,0,2,0),
+               c(0,0,2,0),
+               c(3,3,0,2),
+               c(0,0,3,0))
> rownames(amat)<-V
> colnames(amat)<-V
> 
> stopifnot(dsepAM(1,2,S=NULL,amat) == TRUE)
> stopifnot(dsepAM(1,2,S=4,amat) == FALSE)
> stopifnot(dsepAM(1,2,S=c(3,4),amat) == FALSE)
> 
> proc.time()
   user  system elapsed 
   0.85    0.20    1.04