dendrogram {mva} | R Documentation |

Class `"dendrogram"`

provides general functions for handling
tree-like structures. It is intended as a replacement for similar
functions in hierarchical clustering and classification/regression
trees, such that all of these can use the same engine for plotting or
cutting trees.

The code is still in testing stage and the API may change in the future.

as.dendrogram(object, ...) ## S3 method for class 'dendrogram': plot(x, type = c("rectangle", "triangle"), center = FALSE, edge.root = !is.null(attr(x,"edgetext")), nodePar = NULL, edgePar = list(), xlab = "", ylab = "", horiz = FALSE, frame.plot = FALSE, ...) ## S3 method for class 'dendrogram': cut(x, h, ...) ## S3 method for class 'dendrogram': print(x, digits, ...) ## S3 method for class 'dendrogram': rev(x) ## S3 method for class 'dendrogram': str(object, max.level = 0, digits.d = 3, give.attr = FALSE, wid = getOption("width"), nest.lev = 0, indent.str = "", ...)

`object` |
any R object that can be made into one of class
`"dendrogram"` . |

`x` |
object of class `"dendrogram"` . |

`type` |
type of plot. |

`center` |
logical; if `TRUE` , nodes are plotted centered with
respect to the leaves in the branch. Otherwise (default), plot them
in the middle of all direct child nodes. |

`edge.root` |
logical; if true, draw an edge to the root node. |

`nodePar` |
a `list` of plotting parameters to use for the
nodes (see `points` ) or `NULL` by default which
does not draw symbols at the nodes. The list may contain components
named `pch` , `cex` , `col` , and/or `bg` each of
which can have length two for specifying separate attributes for
inner nodes and leaves. |

`edgePar` |
a `list` of plotting parameters to use for the
edge (see `lines` ). The list may contain components
named `col` , `lty` and/or `lwd` . |

`horiz` |
logical indicating if the dendrogram should be draw
horizontally or not. |

`frame.plot` |
logical indicating if a box around the plot should
be drawn, see `plot.default` . |

`h` |
height at which the tree is cut. |

`..., xlab, ylab` |
graphical parameters, or arguments for other methods. |

`digits` |
integer specifiying the precision for printing, see
`print.default` . |

`max.level, digits.d, give.attr, wid, nest.lev, indent.str` |
arguments to `str` , see `str.default()` . Note that
the default `give.attr = FALSE' still shows `height` and
`members` attributes for each node. |

Warning: This documentation is preliminary.

The dendrogram is directly represented as a nested list where each
component corresponds to a branch of the tree. Hence, the first
branch of tree `z`

is `z[[1]]`

, the second branch of the
corresponding subtree is `z[[1]][[2]]`

etc.. Each node of the tree
carries some information needed for efficient plotting or cutting as
attributes:

`members`

- total number of leaves in the branch
`height`

- numeric non-negative height at which the node is plotted.
`midpoint`

- numeric horizontal distance of the node from
the left border of the branch. This is needed at least for
`plot(*, center=FALSE)`

. `label`

- character; the label of the node
`edgetext`

- character; the label for the edge leading to the node
`nodePar`

- a named list of length one vectors specifying
node-specific attributes for
`points`

plotting, see the`nodePar`

argument above. `edgePar`

- a named list of length one vectors specifying
attributes for
`segments`

plotting of the edge leading to the node, see the`edgePar`

argument above. `leaf`

- logical, if
`TRUE`

, the node is a leaf of the tree.

`cut.dendrogram()`

returns a list with components `$upper`

and `$lower`

, the first is a truncated version of the original
tree, also of class `dendrogram`

, the latter a list with the
branches obtained from cutting the tree, each a `dendrogram`

.

There are `[[`

, `print`

, and `str`

methods for `"dendrogram"`

objects where the first one
(extraction) ensures that selecting sub-branches keeps the class.

Objects of class `"hclust"`

can be converted to class
`"dendrogram"`

using method `as.dendrogram`

.

`isLeaf()`

, `plotNode()`

and `plotNodeLimit()`

are helper
functions.

When using `type = "triangle"`

, `center = TRUE`

often looks
better.

library(mva) data(USArrests) hc <- hclust(dist(USArrests), "ave") (dend1 <- as.dendrogram(hc)) # "print()" method str(dend1) # "str()" method op <- par(mfrow= c(2,2), mar = c(3,3,1,1)) plot(dend1) ## "triangle" type and show inner nodes: plot(dend1, nodePar=list(pch = c(1,NA),cex=0.8), type = "t", center=TRUE) plot(dend1, edgePar=list(col = 1:2, lty = 2:3), edge.root = TRUE) plot(dend1, nodePar=list(pch = 2:1,cex=.4*2:1, col = 2:3), horiz = TRUE) dend2 <- cut(dend1, h=70) plot(dend2$upper) ## leafs are wrong horizontally: plot(dend2$upper, nodePar=list(pch = c(1,7), col = 2:1)) ## dend2$lower is *NOT* a dendrogram, but a list of .. : plot(dend2$lower[[3]], nodePar=list(col=4), horiz = TRUE, type = "tr") ## "inner" and "leaf" edges in different type & color : plot(dend2$lower[[2]], nodePar=list(col=1),# non empty list edgePar = list(lty=1:2, col=2:1), edge.root=TRUE) par(op)