R/node_methods_traversal.R

In data.tree: General Purpose Hierarchical Data Structure

#' Traverse a tree or a sub-tree
#' 
#' Traverse takes the root of a tree or a sub-tree, and "walks" the tree in a specific order. It returns a list of
#' \code{\link{Node}} objects, filtered and pruned by \code{filterFun} and \code{pruneFun}.
#' 
#' @param node the root of a tree or a sub-tree that should be traversed
#' @param traversal any of 'pre-order' (the default), 'post-order', 'in-order', 'level', 'ancestor', or a custom function (see details)
#' @param filterFun allows providing a a filter, i.e. a function taking a \code{Node} as an input, and returning \code{TRUE} or \code{FALSE}.
#' Note that if filter returns \code{FALSE}, then the node will be excluded from the result (but not the entire subtree).
#'
#' @return a list of \code{Node}s
#' 
#' @details
#' The traversal order is as follows. (Note that these descriptions are not precise and complete. They are meant
#' for quick reference only. See the data.tree vignette for a more detailed description). 
#' \describe{
#'    \item{pre-order}{Go to first child, then to its first child, etc.}
#'    \item{post-order}{Go to the first branch's leaf, then to its siblings, and work your way back to the root}
#'    \item{in-order}{Go to the first branch's leaf, then to its parent, and only then to the leaf's sibling}
#'    \item{level}{Collect root, then level 2, then level 3, etc.}
#'    \item{ancestor}{Take a node, then the node's parent, then that node's parent in turn, etc. This ignores the \code{pruneFun} }
#'    \item{function}{You can also provide a function, whose sole parameter is a \code{\link{Node}} object. The
#'    function is expected to return the node's next node, a list of the node's next nodes, or NULL.}
#' }
#' 
#' 
#' @seealso \code{\link{Node}}
#' @seealso \code{\link{Get}}
#' @seealso \code{\link{Set}}
#' @seealso \code{\link{Do}}
#' 
#' @inheritParams Prune
#' 
#' @export
Traverse = function(node, 
                    traversal = c("pre-order", "post-order", "in-order", "level", "ancestor"), 
                    pruneFun = NULL,
                    filterFun = NULL) {
  #traverses in various orders. See https://en.wikipedia.org/wiki/Tree_traversal
  
  nodes <- list()
 
  if(length(traversal) > 1L) {
    traversal <- traversal[1L]
  }
  if(is.function(traversal) || traversal == "pre-order" || traversal == "post-order") {
    
    if (length(pruneFun) == 0 || pruneFun(node)) {
      
      if (is.function(traversal)) {
        children <- traversal(node)
        if (is(children, "Node")) children <- list(children)
        if (is.null(children)) children <- list()
      } else children <- node$children
      
      for(child in children) {
        nodes <- c(nodes, Traverse(child, traversal = traversal, pruneFun = pruneFun, filterFun = filterFun))
      }
      if(length(filterFun) == 0 || filterFun(node)) {
        if(is.function(traversal) || traversal == "pre-order") nodes <- c(node, nodes)
        else nodes <- c(nodes, node)
      }
    }
    
  } else if(traversal == "in-order") {
    if(!node$isBinary) stop("traversal in-order valid only for binary trees")
    if(length(pruneFun) == 0 || pruneFun(node)) {
      if(!node$isLeaf) {
        n1 <- Traverse(node$children[[1]], traversal = traversal, pruneFun = pruneFun, filterFun = filterFun)
        if(length(filterFun) == 0 || filterFun(node)) n2 <- node
        else n2 <- list()
        n3 <- Traverse(node$children[[2]], traversal = traversal, pruneFun = pruneFun, filterFun = filterFun)
        nodes <- c(n1, n2, n3)
      } else {
        if(length(filterFun) == 0 || filterFun(node)) n2 <- node
        else n2 <- list()
        nodes <- c(nodes, n2)
      }
    }
    
  } else if (traversal == "ancestor") {
    
    
    if (!isRoot(node)) {
      nodes <- Traverse(node$parent, traversal = traversal, pruneFun = pruneFun, filterFun = filterFun)
    }
    
    if(length(filterFun) == 0 || filterFun(node)) {
      nodes <- c(node, nodes)
    }
    
  } else if (traversal == "level") {
    
    nodes <- Traverse(node, filterFun = filterFun, pruneFun = pruneFun)
    if (length(nodes) > 0) nodes <- nodes[order(Get(nodes, function(x) x$level))]
    
    
  } else {
    stop("traversal must be pre-order, post-order, in-order, ancestor, or level")
  }
  return (nodes)
}






#' Traverse a Tree and Collect Values
#' 
#' The \code{Get} method is one of the most important ones of the \code{data.tree} package. It lets you traverse a tree
#' and collect values along the way. Alternatively, you can call a method or a function on each \code{\link{Node}}.
#' 
#' @usage 
#' # OO-style:
#' #node$Get(attribute, 
#' #        ..., 
#' #        traversal = c("pre-order", "post-order", "in-order", "level", "ancestor"), 
#' #        pruneFun = NULL, 
#' #        filterFun = NULL, 
#' #        format = FALSE, 
#' #        inheritFromAncestors = FALSE)
#'          
#' # traditional:
#' Get(nodes, 
#'     attribute, 
#'     ..., 
#'     format = FALSE, 
#'     inheritFromAncestors = FALSE, 
#'     simplify = c(TRUE, FALSE, "array", "regular"))
#' 
#' 
#' @param nodes The nodes on which to perform the Get (typically obtained via \code{\link{Traverse}})
#' @param attribute determines what is collected. The \code{attribute} can be
#'       \itemize{
#'         \item a.) the name of a \bold{field} or a \bold{property/active} of each \code{Node} in the tree, e.g. \code{acme$Get("p")} or \code{acme$Get("position")}
#'         \item b.) the name of a \bold{method} of each \code{Node} in the tree, e.g. \code{acme$Get("levelZeroBased")}, where e.g. \code{acme$levelZeroBased <- function() acme$level - 1}
#'         \item c.) a \bold{function}, whose first argument must be a \code{Node} e.g. \code{acme$Get(function(node) node$cost * node$p)}
#'        }
#' @param ... in case the \code{attribute} is a function or a method, the ellipsis is passed to it as additional arguments.
#' @param format if \code{FALSE} (the default), no formatting is being used. If \code{TRUE}, then the first formatter (if any) found along the ancestor path is being used for formatting 
#' (see \code{\link{SetFormat}}). If \code{format} is a function, then the collected value is passed to that function, and the result is returned.
#' @param inheritFromAncestors if \code{TRUE}, then the path above a \code{Node} is searched to get the \code{attribute} in case it is NULL.
#' @param simplify same as \code{\link{sapply}}, i.e. TRUE, FALSE or "array". Additionally, you can specify "regular" if
#' each returned value is of length > 1, and equally named. See below for an example.
#'        
#' @return a vector containing the \code{atrributes} collected during traversal, in traversal order. \code{NULL} is converted
#' to NA, such that \code{length(Node$Get) == Node$totalCount}
#'  
#'  
#' @examples
#' data(acme)
#' acme$Get("level")
#' acme$Get("totalCount")
#'  
#'
#' acme$Get(function(node) node$cost * node$p,
#'          filterFun = isLeaf)
#' 
#' #This is equivalent:
#' nodes <- Traverse(acme, filterFun = isLeaf)
#' Get(nodes, function(node) node$cost * node$p)
#' 
#'    
#' #simplify = "regular" will preserve names
#' acme$Get(function(x) c(position = x$position, level = x$level), simplify = "regular")
#'  
#' @seealso \code{\link{Node}}
#' @seealso \code{\link{Set}}
#' @seealso \code{\link{Do}}
#' @seealso \code{\link{Traverse}}
#'  
#' @import methods
#'  
#' @export
Get = function(nodes, 
               attribute, 
               ..., 
               format = FALSE,
               inheritFromAncestors = FALSE, 
               simplify = c(TRUE, FALSE, "array", "regular")) {
  if (length(nodes) == 0) return(NULL)
  if (!is(nodes, "list")) stop("nodes must be a list of Node objects!")
  simplify <- simplify[1]
                 
  nodes <- unname(nodes)
  if (simplify == "regular") {
    regular = TRUE
    simplify = FALSE
  } else regular = FALSE
  res <- sapply(nodes, 
                function(x) GetAttribute(x, 
                                         attribute, 
                                         ...,
                                         format = format, 
                                         inheritFromAncestors = inheritFromAncestors),
                simplify = simplify
  )
  if (is.character(attribute) && attribute == "name") {
    names(res) <- res
  } else {
    if(is.null(dim(res))){
      names(res) <- Get(nodes, "name")
    } else {
      if(is.null(dimnames(res)))
        dimnames(res) <- list()
      dimnames(res)[[length(dim(res))]] <- Get(nodes, "name")
    } 
  }
  if (regular) {
    res <- do.call(cbind, res)
  }
  
  return (res)
}

#' Executes a function on a set of nodes
#' 
#' @usage 
#' # OO-style:
#' # node$Do(fun, 
#' #         ..., 
#' #         traversal = c("pre-order", "post-order", "in-order", "level", "ancestor"), 
#' #         pruneFun = NULL, 
#' #         filterFun = NULL)
#'          
#' # traditional:
#' Do(nodes, fun, ...)
#' 
#' @param fun the function to execute. The function is expected to be either a Method, or to take a 
#' Node as its first argument
#' @param ... any additional parameters to be passed on to fun
#' 
#' @seealso \code{\link{Node}}
#' @seealso \code{\link{Get}}
#' @seealso \code{\link{Set}}
#' @seealso \code{\link{Traverse}}
#' 
#' @inheritParams Get
#' 
#' @examples 
#' data(acme)
#' traversal <- Traverse(acme)
#' Do(traversal, function(node) node$expectedCost <- node$p * node$cost)
#' print(acme, "expectedCost")
#' 
#' @export
Do <- function(nodes,
               fun, 
               ...) {
  if (length(nodes) == 0) invisible(nodes)
  if (!is(nodes, "list")) stop("nodes must be a list of Node objects!")
      
  for (node in nodes) fun(node, ...)
  
  invisible (nodes)
}




#' Traverse a Tree and Assign Values
#' 
#' The method takes one or more vectors as an argument. It traverses the tree, whereby the values are picked
#' from the vector. Also available as OO-style method on \code{\link{Node}}.
#' 
#' @usage 
#' #OO-style:
#' # node$Set(..., 
#' #          traversal = c("pre-order", "post-order", "in-order", "level", "ancestor"),  
#' #          pruneFun = NULL, 
#' #          filterFun = NULL)
#' #traditional:
#' Set(nodes, ...)
#' 
#' 
#' @param ... each argument can be a vector of values to be assigned. Recycled.
#'
#' @return invisibly returns the nodes (useful for chaining)  
#'  
#' @examples
#' data(acme)
#' acme$Set(departmentId = 1:acme$totalCount, openingHours = NULL, traversal = "post-order")
#' acme$Set(head = c("Jack Brown", 
#'                   "Mona Moneyhead", 
#'                   "Dr. Frank N. Stein", 
#'                   "Eric Nerdahl"
#'                   ),
#'          filterFun = function(x) !x$isLeaf
#'         )
#' print(acme, "departmentId", "head")
#'  
#' @seealso \code{\link{Node}}
#' @seealso \code{\link{Get}}
#' @seealso \code{\link{Do}}
#' @seealso \code{\link{Traverse}}
#'  
#' @inheritParams Get
#'  
#' @export
Set <- function(nodes, 
                ...) {
  
  if (length(nodes) == 0) return(nodes)
  if (!is(nodes, "list")) stop("nodes must be a list of Node objects!")
      
  args <- list(...)
  argsnames <- sapply(substitute(list(...))[-1], deparse)
  gargsnames <- names(args)
  if (is.null(gargsnames)) gargsnames <- vector(mode = "character", length = length(args))
  gargsnames[nchar(gargsnames) == 0] <- argsnames[nchar(gargsnames) == 0]
  names(args) <- gargsnames
  
  
  
  appFun <- function(x, arg, name) {
    x[[name]] <- arg
  }
  
  for(nme in names(args)) {
    arg <- args[[nme]]
    if (length(arg) == 0) arg <- vector("list", 1)
    mapply(appFun, nodes, arg, nme)
  }
  
  invisible (nodes)
  
}