Apply a Function to All Nodes of a Dendrogram

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Description

Apply function FUN to each node of a dendrogram recursively. When y <- dendrapply(x, fn), then y is a dendrogram of the same graph structure as x and for each node, y.node[j] <- FUN( x.node[j], ...) (where y.node[j] is an (invalid!) notation for the j-th node of y.

Usage

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dendrapply(X, FUN, ...)

Arguments

X

an object of class "dendrogram".

FUN

an R function to be applied to each dendrogram node, typically working on its attributes alone, returning an altered version of the same node.

...

potential further arguments passed to FUN.

Value

Usually a dendrogram of the same (graph) structure as X. For that, the function must be conceptually of the form FUN <- function(X) { attributes(X) <- .....; X }, i.e., returning the node with some attributes added or changed.

Note

The implementation is somewhat experimental and suggestions for enhancements (or nice examples of usage) are very welcome. The current implementation is recursive and inefficient for dendrograms with many non-leaves. See the ‘Warning’ in dendrogram.

Author(s)

Martin Maechler

See Also

as.dendrogram, lapply for applying a function to each component of a list, rapply for doing so to each non-list component of a nested list.

Examples

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require(graphics)

## a smallish simple dendrogram
dhc <- as.dendrogram(hc <- hclust(dist(USArrests), "ave"))
(dhc21 <- dhc[[2]][[1]])

## too simple:
dendrapply(dhc21, function(n) utils::str(attributes(n)))

## toy example to set colored leaf labels :
local({
  colLab <<- function(n) {
      if(is.leaf(n)) {
        a <- attributes(n)
        i <<- i+1
        attr(n, "nodePar") <-
            c(a$nodePar, list(lab.col = mycols[i], lab.font = i%%3))
      }
      n
  }
  mycols <- grDevices::rainbow(attr(dhc21,"members"))
  i <- 0
 })
dL <- dendrapply(dhc21, colLab)
op <- par(mfrow = 2:1)
 plot(dhc21)
 plot(dL) ## --> colored labels!
par(op)

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