Hi all,
I am working on a cluster analysis project and I want to implement a
stopping rule for it. At the moment I want to implement the C/H stopping
rule.
Currently I am computing the WGSS like this (in Java):
public static double computeWGSS(DocumentGroup group) {
if (group.getDocuments().size() == 1) {
return 0.0;
}
double wgss = 0.0;
Document[] docs = group.getDocuments();
for (int i = 0; i < docs.length; i++) {
for (int j = i + 1; j < docs.length; j++) {
Document d1 = docs[i];
Document d2 = docs[j];
wgss += computeSumOfSquares(d1.getProfile().getVector(),
d2.getProfile().getVector());
}
}
return wgss / group.size();
}
This is implemented according to C/H's paper "A dendrite method for cluster
analysis".
However I have been unable to find the algorithm for computing BGSS. At the
moment I have implemented it like this:
public static double computeBGSS(List<DocumentGroup> groupList) {
if (groupList.size() == 1) {
return 0.0;
}
double bgss = 0.0;
for (int i = 0; i < groupList.size(); i++) {
for (int j = i + 1; j < groupList.size(); j++) {
DocumentGroup group1 = groupList.get(i);
DocumentGroup group2 = groupList.get(j);
bgss += computeBGSS(group1, group2);
}
}
return bgss;
}
public static double computeBGSS(DocumentGroup group1, DocumentGroup
group2) {
double bgss = 0.0;
for (Document d1 : group1.getDocuments()) {
for (Document d2 : group2.getDocuments()) {
bgss += computeSumOfSquares(d1.getProfile().getVector(),
d2.getProfile().getVector());
}
}
return bgss;
}
Is this implementation correct? When calculating WGSS, we divide the pooled
sum of squares by the number of documents in the cluster, do we have to
divide the pooled sum of squares in BGSS by something, like the number of
clusters?
Thanks in advance,
Behrang Saeedzadeh
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