R/plotDijkstra.R

In locationgamer: Identification of Location Game Equilibria in Networks

#' @title Plot shortest path between two points in a network
#'
#' @description This function plots the entire network and shortest path between two points. The parameter
#' dijkstraPath is obtained by the function dijkstra, in which one has to specify the initial and end node of
#' the path.
#' @param edgeMatrix A matrix containing zeros and ones if an edge between two vertexes is absent or not
#' @param coordMatrix A data frame containing the x and y coordinates of each vertex of the network
#' @param dijkstraPath A vector of numbers corresponding to the vertexes of the shortest path through the network
#' @return Function outputs a two-dimensional plot
#'
#' @examples
#' edgeMatrix <- matrix(0, nrow = 4, ncol = 4)
#' edgeMatrix[,1] <- c(0,1,0,0)
#' edgeMatrix[,2] <- c(1,0,1,1)
#' edgeMatrix[,3] <- c(0,1,0,0)
#' edgeMatrix[,4] <- c(0,1,0,0)
#' coordMatrix <- matrix(c(0,10,15,20,30,30,15,15),ncol = 2)
#' dijkstraPath <- c(4,2,1)
#' plotDijkstra(edgeMatrix, coordMatrix, dijkstraPath)
#'
#' @import graphics
#'
#' @export

plotDijkstra <- function(edgeMatrix, coordMatrix, dijkstraPath){
  minAx <- min(union(coordMatrix[,1], coordMatrix[,2]))
  maxAx <- max(union(coordMatrix[,1], coordMatrix[,2]))
  plot(coordMatrix[,1], coordMatrix[,2], xlim = c(minAx,maxAx), ylim = c(minAx,maxAx), xlab = "X", ylab = "Y")

  for (i in 1:dim(edgeMatrix)[1]){
    for (j in 1: dim(edgeMatrix)[2]){
      if(edgeMatrix[i,j] == 1){
        segments(coordMatrix[i,1], coordMatrix[i,2], coordMatrix[j,1], coordMatrix[j,2] )
      }
    }
  }

  for (i in 1:(length(dijkstraPath)-1)){
    segments(coordMatrix[dijkstraPath[i],1],coordMatrix[dijkstraPath[i],2],coordMatrix[dijkstraPath[i+1],1],coordMatrix[dijkstraPath[i+1],2], col = 'red')
  }

}