pltree.twins             package:cluster             R Documentation

Clustering Tree of a Hierarchical Clustering

Description:

     Draws a clustering tree (dendrogram) of a 'twins' object, i.e.,
     hierarchical clustering, typically resulting from 'agnes()' or
     'diana()'.

Usage:

     ## S3 method for class 'twins':
     pltree(x, main = paste("Dendrogram of ", deparse(x$call)),
                  labels = NULL, ylab = "Height", ...)

Arguments:

       x: an object of class '"twins"', typically created by either
          'agnes()' or 'diana()'.

    main: main title with a sensible default.

  labels: labels to use; the default is constructed from 'x'.

    ylab: label for y-axis.

     ...: graphical parameters (see 'par') may also be supplied as
          arguments to this function.

Details:

     Creates a plot of a clustering tree given a 'twins' object.  The
     leaves of the tree are the original observations.  In case of an
     agglomerative clustering, two branches come together at the
     distance between the two clusters being merged.  For a divisive
     clustering, a branch splits up at the diameter of the cluster
     being splitted.

     Note that currently the method function simply calls
     'plot(as.hclust(x), ...)', which dispatches to 'plot.hclust(..)'. 
     If more flexible plots are needed, consider 'xx <-
     as.dendrogram(as.hclust(x))' and plotting 'xx', see
     'plot.dendrogram'.

Value:

     a NULL value is returned.

See Also:

     'agnes', 'agnes.object', 'diana', 'diana.object', 'hclust', 'par',
     'plot.agnes', 'plot.diana'.

Examples:

     data(votes.repub)
     agn <- agnes(votes.repub)
     pltree(agn)

     dagn  <- as.dendrogram(as.hclust(agn))
     dagn2 <- as.dendrogram(as.hclust(agn), hang = 0.2)
     op <- par(mar = par("mar") + c(0,0,0, 2)) # more space to the right
     plot(dagn2, horiz = TRUE)
     plot(dagn, horiz = TRUE, center = TRUE,
          nodePar = list(lab.cex = 0.6, lab.col = "forest green", pch = NA),
          main = deparse(agn$call))
     par(op)

