R/date_nodes.R

In graemetlloyd/Claddis: Measuring Morphological Diversity and Evolutionary Tempo

#' Returns node ages for a time-scaled tree
#'
#' @description
#'
#' Given a tree with branch-lengths scaled to time and a value for \code{$root.time} will return a vector of node ages.
#'
#' @param time_tree A tree (phylo object) with branch lengths representing time and a value for \code{$root.time}.
#'
#' @details
#'
#' Returns a vector of node ages (terminal and internal) labelled by their node number.
#'
#' @author Graeme T. Lloyd \email{graemetlloyd@@gmail.com}
#'
#' @examples
#'
#' # Create simple four-taxon tree with edge lengths all
#' # set to 1 Ma:
#' time_tree <- ape::read.tree(text = "(A:1,(B:1,(C:1,D:1):1):1);")
#'
#' # Set root.time as 10 Ma:
#' time_tree$root.time <- 10
#'
#' # Get node ages:
#' date_nodes(time_tree = time_tree)
#' @export date_nodes
date_nodes <- function(time_tree) {

  # Need input checks

  # Get N tips:
  n_tips <- ape::Ntip(phy = time_tree)

  # Get N nodes:
  n_nodes <- ape::Nnode(phy = time_tree)

  # Store root node number:
  root_node <- n_tips + 1

  # If tree is a complete polytomy:
  if (time_tree$Nnode == 1) {

    # Create paths for just tips:
    paths <- as.list(x = 1:n_tips)

    # Add root to each path:
    for (i in 1:length(x = paths)) paths[[i]] <- c(paths[[i]], n_tips + 1)

    # If tree is not a complete polytomy:
  } else {

    # Create initial paths list with end nodes (terminal and internal, excluding the root):
    paths <- split(c(1:n_tips, (n_tips + 2):(n_tips + n_nodes)), f = 1:(n_tips + time_tree$Nnode - 1))

    # Strip names:
    names(paths) <- NULL

    # For each path:
    for (i in 1:length(x = paths)) {

      # Set counter as 1:
      j <- 1

      # Identify current node:
      current_node <- paths[[i]][j]

      # While current node is not the root (path has not terminated):
      while (current_node != root_node) {

        # Update current node and add to path:
        current_node <- paths[[i]][j + 1] <- time_tree$edge[match(current_node, time_tree$edge[, 2]), 1]

        # Update counter:
        j <- j + 1
      }
    }
  }

  # Create vector to store node ages:
  date_nodes <- vector(mode = "numeric", length = n_tips + time_tree$Nnode)

  # For each path:
  for (i in 1:length(x = paths)) {

    # Store path lengths from root:
    date_nodes[paths[[i]][1]] <- sum(time_tree$edge.length[match(paths[[i]][1:(length(x = paths[[i]]) - 1)], time_tree$edge[, 2])])
  }

  # Subtract path lengths from root time:
  date_nodes <- time_tree$root.time - date_nodes

  # Add node numbers:
  names(date_nodes) <- 1:(n_tips + time_tree$Nnode)

  # Return node ages:
  return(date_nodes)
}