R/drawTree.R

In dlmtree: Bayesian Treed Distributed Lag Models

#' drawTree
#'
#' @title Draws a new tree structure
#' @description A recursive method for drawing a new tree structure
#'
#' @param depth depth of a tree
#' @param alpha tree shape parameter, 0 < alpha < 1
#' @param beta tree size parameter, beta > 0
#'
#' @returns A integer value of number of terminal nodes
#' @export 
#'
drawTree <- function(depth, alpha, beta) {
  n.term  <- 0
  lp      <- log(alpha) - beta * log(1 + depth)
  if (log(runif(1)) < lp) {
    n.term <- drawTree(depth + 1, alpha, beta) +
      drawTree(depth + 1, alpha, beta)
  } else {
    n.term <- 1
  }
  return(n.term)
}

# hist(sapply(1:10000, function(i) drawTree(0, .5, .5)))