Question

I am using weka kmeans classifier and i have build it a model.Now i want to cluster center value of each centroid.
I get it on weka UI

Attribute    Full Data          0          1
               (48836)    (39469)     (9367)
============================================
tt            428.6238   514.1345    68.3143

How can i get it using weka java jar?

My weka cluster training set has only one attribute.

To get attribute name i do:
String attname =clusterCenters.get(0).attribute(0).name();

How to get value of cluster center?

Answer 1

When you call to the method getClusterCentroids() in SimpleKMeans you get an Instances object (in weka-3-6-8). This is a set of instances that represent your cluster centers (one for each specified cluster).

SimpleKMeans kmeans = ...
// your code
...
Instances instances = kmeans.getClusterCentroids();

Once we have the set of instances (centroids), we can guess its size by numInstances(), iterate through them using instance(int index) and getting their values with double value(int attIndex) this way:

for ( int i = 0; i < instances.numInstances(); i++ ) {
    // for each cluster center
    Instance inst = instances.instance( i );
    // as you mentioned, you only had 1 attribute
    // but you can iterate through the different attributes
    double value = inst.value( 0 );
    System.out.println( "Value for centroid " + i + ": " + value );
}

And that is all.
I have not compiled the code, but that is the way I do it.