/// <summary>
/// Computes cosine similarities between two TermDocumentMatrices.
/// Cosine similarity is defined as (dot product) / (length * length)
/// </summary>
/// <param name="m1">Binary document matrix</param>
/// <param name="m2">tf-idf weighted document matrix</param>
/// <returns>Similarity matrix</returns>
public static TLSimilarityMatrix ComputeCosine(TermDocumentMatrix m1, TermDocumentMatrix m2)
{
TLSimilarityMatrix sims = new TLSimilarityMatrix();
List <TermDocumentMatrix> matrices = TermDocumentMatrix.Equalize(m1, m2);
for (int i = 0; i < m1.NumDocs; i++)
{
TLLinksList links = new TLLinksList();
for (int j = 0; j < m2.NumDocs; j++)
{
double lengthProduct = ComputeLength(matrices[0].GetDocument(i)) * ComputeLength(matrices[1].GetDocument(j));
if (lengthProduct == 0.0)
{
links.Add(new TLSingleLink(m1.GetDocumentName(i), m2.GetDocumentName(j), 0.0));
}
else
{
links.Add(new TLSingleLink(m1.GetDocumentName(i), m2.GetDocumentName(j), ComputeDotProduct(matrices[0].GetDocument(i), matrices[1].GetDocument(j)) / lengthProduct));
}
}
links.Sort();
foreach (TLSingleLink link in links)
{
sims.AddLink(link.SourceArtifactId, link.TargetArtifactId, link.Score);
}
}
return(sims);
}
/// <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);
}
