Transform a dataframe into a tree structure list of lists

dataframe, list, networkd3, r, tree

Solution

Here is a recursive definition:

maketreelist <- function(df, root = df[1, 1]) {
  if(is.factor(root)) root <- as.character(root)
  r <- list(name = root)
  children = df[df[, 1] == root, 2]
  if(is.factor(children)) children <- as.character(children)
  if(length(children) > 0) {
    r$children <- lapply(children, maketreelist, df = df)
    }
  r
  }

canadalist <- maketreelist(df)

That produces what you desire. This function assumes that the first column of the `data.frame` (or `matrix`) you pass in contains the `parent` column and the second column has the `child`. it also takes a `root` parameter which allows you to specify a starting points. It will default to the first parent in the list.

But if you really are interested in playing round with trees. The `igraph` package might be of interest

library(igraph)
g <- graph.data.frame(df)
plot(g)

Problem

I have a data.frame with two columns representing a hierarchical tree, with parents and nodes. I want to transform its structure in a way that I can use as an input for the function `d3tree`, from `d3Network` package. Here's my data frame: ``` df <- data.frame(c("Canada","Canada","Quebec","Quebec","Ontario","Ontario"),c("Quebec","Ontario","Montreal","Quebec City","Toronto","Ottawa")) names(df) <- c("parent","child") ``` And I want to transform it to this structure ``` Canada_tree <- list(name = "Canada", children = list( list(name = "Quebec", children = list(list(name = "Montreal"),list(name = "Quebec City"))), list(name = "Ontario", children = list(list(name = "Toronto"),list(name = "Ottawa"))))) ``` I have succesfully transformed this particular case using this code below: ``` fill_list <- function(df,node) node <- as.character(node)if (is.leaf(df,node)==TRUE){ return (list(name = node)) } else { new_node = df[df[,1] == node,2] return (list(name = node, children = list(fill_list(df,new_node[1]),fill_list(df,new_node[2])))) } ``` The problem is, it only works with trees which every parent node has exactly two children. You can see I hard coded the two children (new_node[1] and new_node[2]) as inputs for my recursive function. I'm trying to figure out a way that I could call the recursive function as many time as the parent's node children. Example: ``` fill_list(df,new_node[1]),...,fill_list(df,new_node[length(new_node)]) ``` I tried these 3 possibilities but none of it worked: First: Creating a string with all the functions and parameters and then evaluating. It return this error `could not find function fill_functional(df,new_node[1])`. That's because my function wasn´t created by the time I called it after all. ``` fill_functional <- function(df,node) { node <- as.character(node) if (is.leaf(df,node)==TRUE){ return (list(name = node)) } else { new_node = df[df[,1] == node,2] level <- length(new_node) xxx <- paste0("(df,new_node[",seq(level),"])") lapply(xxx,function(x) eval(call(paste("fill_functional",x,sep="")))) } } ``` Second: Using a for loop. But I only got the children of my root node. ``` L <- list() fill_list <- function(df,node) { node <- as.character(node) if (is.leaf(df,node)==TRUE){ return (list(name = node)) } else { new_node = df[df[,1] == node,2] for (i in 1:length(new_node)){ L[i] <- (fill_list(df,new_node[i])) } return (list(name = node, children = L)) } } ``` Third: Creating a function that populates a list with elements that are functions, and just changing the arguments. But I wasn't able to accomplish anything interesting, and I'm afraid I'll have the same problem as I did on my first try described above.

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