public IEnumerable<KeyValuePair<int, double>> Rank(IEnumerable<string> queryTerms, SortedDictionary<string, Term> terms, int documentCount)
{
SortedList<int, double> scores = new SortedList<int, double>();
foreach (var queryTerm in queryTerms)
{
if (!terms.ContainsKey(queryTerm))
return null;
Term currentTerm = terms[queryTerm];
int documentFrequency = currentTerm.Frequency;
foreach (var posting in currentTerm.Postings)
{
int docId = posting.Key;
int termFrequency = posting.Value;
double weight = GetTfIdf(termFrequency, documentCount, documentFrequency);
if (scores.ContainsKey(docId))
{
scores[docId] += weight;
}
else
{
scores.Add(docId, weight);
}
}
}
return scores.OrderByDescending(kvp => kvp.Value);
}