R/compareShortestPath.R

In netDx: Network-based patient classifier

#' compare intra-cluster shortest distance to overall shortest distance of the
#'  network
#'
#' @details Uses Dijkstra's algorithm for weighted edges. Pairwise nodes with
#' infinite distances are excluded before computing average shortest path 
#' for a network. This function requires the igraph package to be installed.
#' @param net (data.frame) network on which to compute shortest path. 
#' SOURCE, TARGET, WEIGHTS. 
#' Column names are ignored but expects a header row. Distances will be 
#' computed based on the third column
#' @param pheno (data.frame) Node information. ID (node name) and GROUP
#' (cluster name)
#' @param plotDist (logical) if TRUE, creates a violin plot showing the 
#' shortest path distributions for each group.
#' @param verbose (logical) print messages
#' @import ggplot2
#' @importFrom combinat combn
#' @examples data(silh); 
#' colnames(silh$net)[3] <- 'weight'
#' compareShortestPath(silh$net, silh$groups)
#' @return (list) Two lists, 'avg' and 'all'. keys are cluster names. 
#' values for 'avg' are mean shortest path ; for 'all', are all pairwise
#' shortest paths
#' for subnetworks that contain only the edges where source and target both 
#' belong to the corresponding cluster. In addition, there is an 'overall' 
#' entry for the mean shortest distance for the entire network.
#' @importFrom stats sd
#' @export
compareShortestPath <- function(net, pheno, plotDist = FALSE, verbose = TRUE) {
    colnames(net) <- c("source", "target", "weight")
    
    if (verbose) {
        message("Weight distribution:")
        print(summary(net[, 3]))
    }
    
    .getAvgD <- function(mat) {
        tmp <- mat[upper.tri(mat, diag = FALSE)]
        idx <- which(is.infinite(tmp))
        if (any(idx)) 
            tmp <- tmp[-idx]
        ## if (verbose) message(sprintf('\tN=%i distances\n', length(tmp)))
        
        c(mean(tmp, na.rm = TRUE), sd(tmp, na.rm = TRUE), length(tmp))
    }
    
    .getAllD <- function(mat) {
        tmp <- mat[upper.tri(mat, diag = FALSE)]
        idx <- which(is.infinite(tmp))
        if (any(idx)) 
            tmp <- tmp[-idx]
        tmp
    }
    
    g <- igraph::graph_from_data_frame(net, vertices = pheno$ID)
    d_overall <- igraph::shortest.paths(g, algorithm = "dijkstra")
    if (verbose) message(sprintf("Overall: %i nodes", length(pheno$ID)))
    tmp <- .getAvgD(d_overall)
    if (verbose) {
    	message(sprintf("All-all shortest path = %2.3f (SD=%2.3f)", 
				tmp[1], tmp[2]))
   		message(sprintf("(N=%i distances)", tmp[3]))
		}
    
    cnames <- unique(pheno$GROUP)
    dset <- list()
    dall <- list()
    for (curr_cl in cnames) {
        cl <- pheno$ID[which(pheno$GROUP %in% curr_cl)]
        if (verbose) {
            message(sprintf("\n%s: N=%i nodes", curr_cl, length(cl)))
				}
        
        # subgraph with intra-cluster connections
				tmp <- net[which(net[, 1] %in% cl & net[,2] %in% cl),] 
        g2 <- igraph::graph_from_data_frame(d = tmp,vertices = cl)
        tmp <- igraph::shortest.paths(g2, algorithm = "dijkstra")
        if (verbose) message(sprintf("%s", curr_cl))
        dset[[curr_cl]] <- .getAvgD(tmp)
        dall[[curr_cl]] <- .getAllD(tmp)
        tmp <- dset[[curr_cl]]
        if (verbose) {
         	message(sprintf("\t%s-%s: Mean shortest = %2.3f (SD= %2.3f)", 
						curr_cl, curr_cl, tmp[1], tmp[2]))
        	message("(N=%i dist)", tmp[3])
				}
    }
    
    # now repeat for all pairwise classes
    cpairs <- as.matrix(combinat::combn(cnames, 2))
    if (verbose) message("Pairwise classes:")
    for (k in seq_len(ncol(cpairs))) {
        type1 <- pheno$ID[which(pheno$GROUP %in% cpairs[1, k])]
        type2 <- pheno$ID[which(pheno$GROUP %in% cpairs[2, k])]
        idx <- which(net[, 1] %in% type1 & net[, 2] %in% type2)
        idx2 <- which(net[, 1] %in% type2 & net[, 2] %in% type1)
        idx <- c(idx, idx2)
        g <- igraph::graph_from_data_frame(d = net[idx, ])
        tmp <- igraph::shortest.paths(g, algorithm = "dijkstra")
        cur <- sprintf("%s-%s", cpairs[1, k], cpairs[2, k])
        dset[[cur]] <- .getAvgD(tmp)
        # dset[[curr_cl]] <- .getAvgD(tmp)
        dall[[cur]] <- .getAllD(tmp)
        
        tmp <- dset[[curr_cl]]
        if (verbose)  {
          message(sprintf("\t%s-%s: Mean shortest = %2.3f (SD= %2.3f)", 
						cpairs[1,k], cpairs[2, k], tmp[1], tmp[2]))
        	message(sprintf("(N=%i dist)", tmp[3]))
				}
    }
    
    dset[["overall"]] <- .getAvgD(d_overall)
    dall[["overall"]] <- .getAllD(d_overall)
    
    out <- list(avg = dset, all = dall)
    if (plotDist) {
        par(las = 1, bty = "n")
        dl <- data.frame(intType = rep(names(dall), 
							lapply(dall, length)), dijk = unlist(dall))
        plotList <- list()
        p <- ggplot(dl, aes(dl[,"intType"], dl[,"dijk"]))
        p <- p + ylab("Pairwise Dijkstra distance\n(smaller is better)")
        p <- p + xlab("Pair groups")
        p2 <- p + geom_violin(scale = "width") + geom_boxplot(width = 0.02)
        print(p2)
        out[["plot"]] <- p2
    }
    return(out)
    
}