R/amat.R

In causalDisco: Tools for Causal Discovery on Observational Data

#' Extract adjacency matrix from tpdag, cpdag, tpag or pag object
#' 
#' If the input is a tpdag or cpdag, the resulting adjacency matrix A is "from-to"
#' matrix encoded as follows: 
#'     - A(i,j) = 1 and A(j,i) = 0 means there is an edge j -> i.
#'     - A(j,i) = 1 and A(i,j) = 0 means there is an edge i -> j. 
#'     - A(i,j) = 1 and A(j,i) = 1 means there is an undirected edge between i and j, i - j. 
#'     - A(i,j) = 0 and A(j,i) = 0 means there is no edge between i and j. 
#' 
#' If the inout is a tpag or pag, there are four possible entry values: 0 (no edge), 1 (circle),
#' 2 (arrowhead), 3 (tail). It is still encoded as a "to-from" adjacency matrix, which means
#' that e.g. A(i,j) = 1 places a circle in the directed from j to i. For example, if 
#' A(i,j) = 1 and A(j,i) = 2, we have that i o-> j. Similarly, A(i,j) = 2 and A(j,i) = 3 
#' mean that i <- j. 
#' 
#' @param x \code{tpdag}, \code{cpdag}, \code{tpag}, or \code{pag} object as obtained
#' from \link{tpc}, \link{pc}, \link{tfci}, or \link{fci}, respectively. 
#' 
#' @export
amat <- function(x) {
  x_class <- class(x) 
  
  if (any(c("tpdag", "tpag") %in% x_class)) {
      out <- x$tamat
  } else if (any(c("cpdag", "pag") %in% x_class)) {
    out <- x$amat
  }
  
  out
}