DMST procedure

Gives a high resolution plot of an ordination with minimum spanning tree (A.W.A. Murray).


Options

DIMENSIONS = scalars
Two numbers specifying the dimensions to display, allowed values 1...5

TITLE = text
Title for the graph

WINDOW = scalar
Window for the graph; default 1

KEYWINDOW = scalar
Window for the key; default 2

SCREEN = string
Controls screen (clear, keep); default clea


Parameters

COORDINATES = matrices or datamatrices
Coordinates from ordination

TREE = matrices
Minimum spanning tree

SIMILARITY = symmetric matrices
Association matrix used to derive ordination

SYMBOLS = factors or texts
Symbols to label the coordinates

PENCOORDINATES = scalars
Pen to use for the coordinates

PENTREE = scalars
Pen to use for the minimum spanning tree


Description

DMST plots a minimum spanning tree using coordinates saved, for example, from a PCO. The COORDINATES parameter specifies the coordinates for the units in the plot, using either a matrix or a pointer to a set of variates (that is, a "datamatrix"). The minimum spanning tree can be supplied using the TREE parameter, or it can be calculated from the original association matrix specified using the SIMILARITY parameter. If TREE supplies a matrix with no values, these will be set to the tree calculated from the SIMILARITY matrix. If the COORDINATES structure was originally declared with row labels the procedure will automatically use these to label the plots. Alternative symbols can be defined using the SYMBOLS parameter. You can also specify the pens to be used to plot the coordinates and tree, using parameters PENCOORDINATES and PENTREE respectively. The definition of these pens, outside the procedure, thus allows the colour, size, font and linestyle of links in the tree to be controlled. By default the coordinates are plotted with colour 1 and the tree with colour 2, symbols are 0.8 of normal size, and the tree is plotted with a dotted line.

   Options TITLE, WINDOW, KEYWINDOW and SCREEN function as usual for high resolution graphics. If the WINDOW is unset a default layout with appropriately labelled axes is produced in window 1. Axes will be scaled automatically unless limits have already been set outside the procedure.


Options: DIMENSIONS, TITLE, WINDOW, KEYWINDOW, SCREEN.

Parameters: COORDINATES, TREE, SIMILARITY, SYMBOLS, PENCOORDINATES, PENTREE.


Method

A two dimensional representation of the results of a multivariate analysis, such as a PCO, is plotted on the current high resolution graphics device. A minimum spanning tree is calculated (by HDISPLAY) from an input similarity matrix if not supplied. The tree is superimposed on the plot. The procedure uses GETATTRIBUTE to access the row labels (if any) of the input structures. The input structures are converted to variates if necessary and DGRAPH is used to plot the desired data.


Action with RESTRICT

Restrict is irrelevant with matrix input structures. It should work as expected with variates.