| Statistics Toolbox | |
Syntax
H = dendrogram(Z) H = dendrogram(Z,p) [H,T] = dendrogram(...)
Description
H = dendrogram(Z)
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 upside-down, 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)
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 size m that contains the cluster number for each object in the original dataset. T provides access to the nodes of a cluster hierarchy that are not displayed in the dendrogram because they fall below the cutoff value p. For example, to find out which objects are contained in leaf node k of the dendrogram, use find(T==k). Leaf nodes are the nodes at the bottom of the dendrogram that have no other nodes below them.
When there are fewer than p objects in the original data, all objects are displayed in the dendrogram. In this case, T is the identical map, i.e., T = (1:m)', where each node contains only itself.
Example
rand('seed',12);
X= rand(100,2);
Y= pdist(X,'citiblock');
Z= linkage(Y,'average');
[H, T] = dendrogram(Z);
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.
See Also
cluster, clusterdata, cophenet, inconsistent, linkage, pdist, squareform
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