/// <summary>
/// Computes Jensen-Shannon divergence on two TermDocumentMatrices
/// </summary>
/// <param name="source">Source artifacts collection</param>
/// <param name="target">Target artifacts collection</param>
/// <returns>Similarity matrix</returns>
public static TLSimilarityMatrix Compute(TermDocumentMatrix source, TermDocumentMatrix target)
{
List <TermDocumentMatrix> matrices = TermDocumentMatrix.Equalize(source, target);
TLSimilarityMatrix sims = new TLSimilarityMatrix();
for (int i = 0; i < matrices[0].NumDocs; i++)
{
TLLinksList list = new TLLinksList();
for (int j = 0; j < matrices[1].NumDocs; j++)
{
list.Add(new TLSingleLink(matrices[0].GetDocumentName(i), matrices[1].GetDocumentName(j),
DocumentSimilarity(matrices[0].GetDocument(i), matrices[1].GetDocument(j))));
}
list.Sort();
foreach (TLSingleLink link in list)
{
sims.AddLink(link.SourceArtifactId, link.TargetArtifactId, link.Score);
}
}
return(sims);
}
/// <summary>
/// Computes cosine similarities between a set of boolean document vectors and a tfidf weighted corpus
/// </summary>
/// <param name="ids">Boolean document vectors</param>
/// <param name="tfidf">tf-idf weighted document vectors</param>
/// <returns>Similarity matrix</returns>
private static TLSimilarityMatrix ComputeSimilarities(TermDocumentMatrix ids, TermDocumentMatrix tfidf)
{
TLSimilarityMatrix sims = new TLSimilarityMatrix();
List <TermDocumentMatrix> matrices = TermDocumentMatrix.Equalize(ids, tfidf);
for (int i = 0; i < ids.NumDocs; i++)
{
TLLinksList links = new TLLinksList();
for (int j = 0; j < tfidf.NumDocs; j++)
{
double product = 0.0;
double asquared = 0.0;
double bsquared = 0.0;
for (int k = 0; k < matrices[0].NumTerms; k++)
{
double a = matrices[0][i, k];
double b = matrices[1][j, k];
product += (a * b);
asquared += Math.Pow(a, 2);
bsquared += Math.Pow(b, 2);
}
double cross = Math.Sqrt(asquared) * Math.Sqrt(bsquared);
if (cross == 0.0)
{
links.Add(new TLSingleLink(ids.GetDocumentName(i), tfidf.GetDocumentName(j), 0.0));
}
else
{
links.Add(new TLSingleLink(ids.GetDocumentName(i), tfidf.GetDocumentName(j), product / cross));
}
}
links.Sort();
foreach (TLSingleLink link in links)
{
sims.AddLink(link.SourceArtifactId, link.TargetArtifactId, link.Score);
}
}
return(sims);
}
