R/DetermineInteractionTypeOfPath.r

In CausalR: Causal network analysis methods

#' @title determine interaction type of path
#' @description 
#' Determines the sign of a given path.
#' Given a path and through the network, this function will determine if the path results in activation or inhibition.
#' Activation is indicated by 1, inhibition by -1 

#' @param network an igraph representing the network
#' @param nodesInPath an ordered list of the nodes visited on the path - note that these contain numbers which use 
#'     R's internal reference to the edges
#' @return a signed integer representing the paths sign

DetermineInteractionTypeOfPath <- function(network, nodesInPath) {
    # network must be an igraph nodesInPath is an ordered list of the nodes visited on the path - note that these contain numbers which use R's internal
    # reference to the edges
    
    numEdges <- length(nodesInPath[[1]]) - 1
    # Declare a variable that will store the numerical references for the edges in a path
    nodeEdges <- matrix(0, 1, numEdges)
    
    for (i in 1:numEdges) {
        # Get the R's edge number for two successive nodes in nodesInPath
        nodeEdges[i] <- igraph::E(network)[igraph::`%->%`(nodesInPath[[1]][i], nodesInPath[[1]][i + 1])][[1]]
    }
    # Take the product of the weights for each edge in the path to get the overall interaction
    netPathInteraction = prod(igraph::edge_attr(network, "Weight", nodeEdges))
    
    return(netPathInteraction)
}