MATLAB: Determining the optimal number of clusters in Kmeans technique

Question

I have a matrix like "A". I want to cluster its data using K-Means method.

A=[45  58  59
46  76  53
57  65  71
40  55  59
25  35  42
34  51  74
46  90  53
46  63  60
33  50  78
53  57  60
31  28  72
49  49  53
76  88  82
34  100  198
35  35  35];

I used the following command to cluster data.

[Data_clustred, c]= kmeans(A,num_cluster);

by the way, knowing the optimal number of cluster is neccessary to me.

Is there any criteria that determines the optimal numbers of clusters? if so, How can I write its programm.

any help whould be appreciated. Thanks in advance.

Answer 1

http://www.mathworks.com/matlabcentral/answers/34623-how-to-determine-the-optimum-number-of-cluster-use-k-mean-clustering