R/Add_boundary_points.R

In muHVT: Constructing Hierarchical Voronoi Tessellations and Overlay Heatmap for Data Analysis

Add_boundary_points <-
function (tile.child, tile.parent, data.points) {
  desired_index <- c()
  dist_to_tile_endpoints <- list()
  #for all the vertices in the parent tile
  for (m in 1: length(tile.parent$x)) {
    #for all the centroids of the child tile.
    for (n in 1: length(data.points[, 1])) {
      #find out the distance of each vertex from the all the centroids of the child tile
      dist_to_tile_endpoints[[n]] <- sum(((tile.parent$x[m] - data.points[n, 1]) ^ 2),
                                         ((tile.parent$y[m] - data.points[n, 2]) ^ 2))
    }
    # index of the child tile to which the vertex of the parent tile belongs is the one to which
    # the vertex of the parent tile is closest
    desired_index <- which(dist_to_tile_endpoints == min(as.numeric(dist_to_tile_endpoints)))
    #if more than one centroid of the child is close to a given vertex then it should be
    #added to all those child tiles.
    for(i in 1: length(desired_index)){
      tile.x <- c(tile.child[[desired_index[i]]]$x, tile.parent$x[m])
      tile.y <- c(tile.child[[desired_index[i]]]$y, tile.parent$y[m])
      tile.bp <- c(tile.child[[desired_index[i]]]$bp, tile.parent$bp[m])
      #use only those points which form a convex hull
      var1 <- grDevices::chull(tile.x,tile.y)
      tile.child[[desired_index[i]]]$x <- tile.x[var1]
      tile.child[[desired_index[i]]]$y <- tile.y[var1]
      tile.child[[desired_index[i]]]$bp <- tile.bp[var1]
    }
  }
  return (tile.child)
}