# [R] accessing the "address" of items in a recursive list

phlow florian.kleedorfer at austria.fm
Tue Jan 22 15:43:13 CET 2008

```

j daniel wrote:
>
>
> I would like to print the "address" of the smaller dendrograms on the edge
> similar to this:
>
>       if(!is.leaf(n)) {
>         attr(n, "edgetext") <- paste("height of",(attr(n,"height"))
>       }
>       n
> }
>
> Where "i,j,k" is printed instead of "height".  But I have not been able to
> figure out how to ask each dendrogram its address within the dendrapply
> function.  Can anyone help me with this?
>
>
Hi!

Load the following four functions into R and execute this (assuming your
dendrogram is in variable 'dend')

newdend <- dendrapplyGlobal(dend,
"height",function(x){names(x)},attrNameTo="edgetext")

#From the specified dendrogram X a vector of all values of the specified
#node attribute is extracted, modified by the function FUN and a new
#dendrogram is created using the new values for the attribute. Optionally,
#a different attribute can be set using 'attrNameTo'
dendrapplyGlobal <- function(X,attrName,FUN,...,attrNameTo=NULL) {
if (is.null(attrNameTo)) {
attrNameTo <- attrName
}
funcGet <- function(x){
attr(x,attrName)
}
funcSet <- function(x,value){
attr(x,attrNameTo) <- value
return(x)
}
values <- dendrapplyToVector(X,funcGet)
values <- FUN(values,...)
ret <- dendrapplyFromVector(X,values,funcSet)
return(ret)
}

#Traverses the dendrogram in postorder and applies FUN to each node.
#The result of each evaluation is stored in the resulting array.
#Additional arguments to FUN can be passed as ...
#The names attribute of the resulting vector is the 'path' to each node.
#This implementation is based on dendrapply(graphics).
dendrapplyToVector <- function(X,FUN,...) {
FUN <- match.fun(FUN)
if (!inherits(X, "dendrogram"))
stop("'X' is not a dendrogram")
Napply <- function(d,path="") {
if (is.leaf(d)) {
ret <- c(FUN(d,...))
names(ret)[1] <- substr(path,start=1,stop=nchar(path)-1)
return(ret)
}
ret <- vector()
for (j in seq_along(d)) {
}
ret <- append(ret,FUN(d,...))
names(ret)[length(ret)] <- substr(path,start=1,stop=nchar(path)-1)
return(ret)
}
Napply(X)
}

#Traverses the dendrogram X in postorder and constructs a new dendrogram
using
#the specified function FUN and vector parVec. Each element of parVec must
#relate to a node in X, which is the case if parVec was created using
#dendrapplyToVector().
#Additional arguments to FUN can be passed as ...
#This implementation is based on dendrapply(graphics).
dendrapplyFromVector <- function(X,parVec,FUN,...) {
FUN <- match.fun(FUN)
if (!inherits(X, "dendrogram"))
stop("'X' is not a dendrogram")
Napply <- function(d,v) {
if (is.leaf(d)) {
ret <- FUN(d,v,...)
return(ret)
} else {
ret <- d
if (!is.list(ret))
ret <- as.list(ret)
i <- 1
for (j in seq_along(d)) {
childrenCount <- getDendrogramNodeCount(d[[j]])
indices <- i:(i+childrenCount-1)
ret[[j]] <- Napply(d[[j]],v[indices])
i <- i + childrenCount
}
ret <- FUN(ret,v[i],...)
}
return(ret)
}
Napply(X,parVec)
}

#Returns the number of nodes in a dendrogram.
getDendrogramNodeCount <- function(dend) {
if (!is.leaf(dend)){
childrenSum <- 0
for (child in dend) {
childrenSum <- childrenSum + getDendrogramNodeCount(child)
}
return(childrenSum+1)
}
return(1)
}

hth,
Florian

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