dendrapply {stats} R Documentation

## Apply a Function to All Nodes of a Dendrogram

### 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

```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

`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

```require(graphics)

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

## 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)
```

[Package stats version 3.5.0 Index]