dendrogram (Statistics Toolbox)

Plot dendrogram graphs

Syntax

H = dendrogram(Z) 
H = dendrogram(Z,p)
[H,T] = dendrogram(...)
[H,T,perm] = dendrogram(...)
[...] =  dendrogram(...,'colorthreshold',t)
[...] = dendrogram(...,'orientation','orient')

Description

H = dendrogram(Z) generates a dendrogram plot of the hierarchical, binary cluster tree, Z. Z is an (m-1)-by-3 matrix, generated by the linkage function, where m is the number of objects in the original dataset.

A dendrogram consists of many U-shaped lines connecting objects in a hierarchical tree. Except for the Ward linkage (see linkage), the height of each U represents the distance between the two objects being connected. The output, H, is a vector of line handles.

H = dendrogram(Z,p) generates a dendrogram with only the top p nodes. By default, dendrogram uses 30 as the value of p. When there are more than 30 initial nodes, a dendrogram may look crowded. To display every node, set p = 0.

[H,T] = dendrogram(...) generates a dendrogram and returns T, a vector of length m that contains the leaf node number for each object in the original dataset. T is useful when p is less than the total number of objects, so some leaf nodes in the display correspond to multiple objects. For example, to find out which objects are contained in leaf node k of the dendrogram, use find(T==k). When there are fewer than p objects in the original data, all objects are displayed in the dendrogram. In this case, T is the identity map, i.e., T = (1:m)', where each node contains only itself.

When there are fewer than p objects in the original data, all objects are displayed in the dendrogram. In this case, T is the identity map, i.e., T = (1:m)', where each node contains only itself.

[H,T,perm] = dendrogram(...) generates a dendrogram and returns the permutation vector of the node labels of the leaves of the dendrogram. perm is ordered from left to right on a horizontal dendrogram and bottom to top for a vertical dendrogram.

[...] = dendrogram(...,'colorthreshold',t) assigns a unique color to each group of nodes in the dendrogram where the linkage is less than the threshold t. t is a value in the interval [0,max(Z(:,3))]. Setting t to the string 'default' is the same as t = .7(max(Z(:,3))). 0 is the same as not specifying 'colorthreshold'. The value max(Z(:,3)) treats the entire tree as one group and colors it all one color.

[...] = dendrogram(...,'orientation','orient') orients the dendrogram within the figure window. The options for 'orient' are

'top'
Top to bottom (default)

'bottom'
Bottom to top

'left'
Left to right

'right'
Right to left

`'top'`	Top to bottom (default)
`'bottom'`	Bottom to top
`'left'`	Left to right
`'right'`	Right to left

Example

rand('seed',12);
X= rand(100,2);
Y= pdist(X,'cityblock');
Z= linkage(Y,'average');
[H,T] = dendrogram(Z,'colorthreshold','default');


find(T==20)
ans =
    20
    49
    62
    65
    73
    96

This output indicates that leaf node 20 in the dendrogram contains the original data points 20, 49, 62, 65, 73, and 96.

dcovary disttool