R/GetShortestPathsFromCCG.r

In CausalR: Causal network analysis methods

#' @title get shortest paths from CCG
#' @description
#' Gets the node names in the shortest path from one node in a CCG to another
#' @param network built from iGraph
#' @param hypothesisnode hypothesis node ID
#' @param targetnode target node ID
#' @param showbothdirs where multiple paths from a positive and negative node, FALSE returns only the shortest. Otherwise both are returned.
#' @param quiet a flag to suppress output to console. FALSE by default.
#' @return a list of vectors containing the nodes of individual paths
#' @export
#' @concept CausalR
#' @examples
#' network <- system.file(package='CausalR', 'extdata', 'testNetwork.sif')
#' ccg = CreateCCG(network)
#' hypothesisnode = 1
#' targetnode = 10
#' GetShortestPathsFromCCG (ccg, hypothesisnode, targetnode)


GetShortestPathsFromCCG <- function(network, hypothesisnode, targetnode, showbothdirs = FALSE, quiet = FALSE) {
    
    if (is.numeric(hypothesisnode)) {
        hypothesis <- hypothesisnode
    } else {
        hypothesis <- GetNodeID(network, hypothesisnode)
    }
    
    if (is.numeric(targetnode)) {
        targetID <- targetnode
    } else {
        targetID <- which(igraph::V(network)$unsignedName == targetnode)
        if (!any(targetID)) {
            targetID <- which(igraph::V(network)$name == targetnode)
        }
    }
    
    shortestPath <- igraph::distances(network, hypothesis, targetID, mode = "out")
    
    # If there are no paths from hypothesis to target (+ or -), return NULL
    if (all(shortestPath == Inf)) {
        return(NULL)
    }
    
    # If there is more than one target (i.e. a + and a - node), decide which one(s) to include: - don't include one which has no path from the
    # hypothesis node - include the one which is closer to the hypothesis node (both if the two paths are equal) - include the one which is further from
    # the hypothesis node if showbothdirs is true (i.e. flag to override the default 'show only the closer node' behaviour)
    if (length(shortestPath) > 1) {
        if (shortestPath[1] == Inf) {
            targetID <- targetID[2]
        } else {
            if (shortestPath[2] == Inf) {
                targetID <- targetID[1]
            } else {
                if (!showbothdirs) {
                    if (shortestPath[1] < shortestPath[2]) {
                        targetID <- targetID[1]
                    } else {
                        if (shortestPath[2] < shortestPath[1]) {
                            targetID <- targetID[2]
                        }
                    }
                }
            }
        }
    }
    
    # Now assemble a list of the nodes in the paths from the hypothesis to the targets selected above
    nodesinpath <- list()
    inode <- 0
    for (itarget in 1:length(targetID)) {
        shortestPaths <- igraph::all_shortest_paths(network, hypothesis, targetID[itarget], mode = "out")
        for (i in 1:length(shortestPaths$res)) {
            inode <- inode + 1
            nodesinpath[[inode]] <- igraph::V(network)$name[shortestPaths$res[[i]]]
        }
    }
    
    if (!quiet) {
        for (i in 1:length(nodesinpath)) {
            for (j in 1:length(nodesinpath[[i]])) {
                cat(nodesinpath[[i]][j], "\t", sep = "")
            }
            cat("\b\n")
        }
        return(invisible(nodesinpath))
    } else {
        return(nodesinpath)
    }
}