/// <summary>
/// Creates and returns a new NGramDictionary from a string.<br />
/// This string must be produced by the ToString() method of a NGramDictionary object.
/// </summary>
/// <param name="str">A string produced by the ToString() method of a NGramDictionary object.</param>
/// <returns>A new NGramDictionary object</returns>
public static NGramDictionary DeserializeFrom(string str)
{
string[] lines = str.Split('\n');
int minNGram = Int32.Parse(lines[0].Split('\t')[0]);
int maxNGram = Int32.Parse(lines[0].Split('\t')[1]);
IDictionary <NGram, int> nGrams = new Dictionary <NGram, int>();
var extractor = new NGramExtractor(minNGram, maxNGram);
foreach (string line in lines.Skip(1))
{
string[] row = line.Split('\t');
var nGram = new NGram(row[0].Split(null));
int freq = Int32.Parse(row[1]);
if (!nGrams.ContainsKey(nGram))
{
nGrams.Add(nGram, freq);
}
}
return(new NGramDictionary(extractor, nGrams));
}
/// <summary>
/// returns frequency of the n-gram which consists of nGramTokens
/// </summary>
/// <param name="nGramTokens">Tokens of the n-gram</param>
/// <returns></returns>
public int GetFrequency(params string[] nGramTokens)
{
Validate(nGramTokens);
var nGram = new NGram(nGramTokens);
return(GetFrequency(nGram));
}
/// <summary>
/// returns requency of the n-gram
/// </summary>
/// <param name="nGram"></param>
/// <returns></returns>
public int GetFrequency(NGram nGram)
{
if (nGrams.ContainsKey(nGram))
{
return(nGrams[nGram]);
}
return(0);
}
private IEnumerable <NGram> GetNGrams(IList <string> tokens, int index)
{
var nGrams = new List <NGram>();
int maxWindowSize = Math.Min(tokens.Count() - index, maxNGramSize);
for (int windowSize = minNGramSize; windowSize <= maxWindowSize; windowSize++)
{
NGram nGram = GetNGram(tokens, index, windowSize);
nGrams.Add(nGram);
}
return(nGrams);
}
public double GetMLE(NGram denominatorNGram, NGram nominatorNGram)
{
int nom = nGramDictionary.GetFrequency(nominatorNGram);
int denom = nGramDictionary.GetFrequency(denominatorNGram);
if (denom == 0)
{
return(0);
}
return(nom / (double)denom);
}
public double GetSentenceProbability(IList <string> tokens)
{
if (maxNGramSize == 1)
{
return(GetSentenceProbabilityForUnigrams(tokens));
}
List <string> tokenList = tokens.ToList();
AddStartStopSymbols(tokenList);
var ext = new NGramExtractor(maxNGramSize - 1, maxNGramSize);
IList <NGram> nGrams = ext.ExtractAsList(tokenList);
nGrams.RemoveAt(nGrams.Count - 1);
double logP = 0;
for (int i = 0; i < nGrams.Count; i += 2)
{
double p = GetMLE(nGrams[i], nGrams[i + 1]);
logP += Math.Log10(p);
NGram x = nGrams[i];
//Console.WriteLine(nGrams[i + 1] + "/" + nGrams[i] + ":" + Math.Log10(p));
//Console.WriteLine(nGrams[i] + ":" + Math.Log10(GetUnigramMLE(nGrams[i])));
}
//double p = 1;
//for (int i = 0; i < nGrams.Count; i += 2)
//{
// p *= GetMLE(nGrams[i], nGrams[i + 1]);
//}
//return p;
return(logP);
}
public double GetUnigramMLE(NGram nGram)
{
return(nGramDictionary.GetFrequency(nGram) / (double)tokenCount);
}
private bool Equals(NGram other)
{
return(Tokens.SequenceEqual(other.Tokens));
}
/// <summary>
/// Creates and returns a new NGramDictionary from a string.<br />
/// This string must be produced by the ToString() method of a NGramDictionary object.
/// </summary>
/// <param name="str">A string produced by the ToString() method of a NGramDictionary object.</param>
/// <returns>A new NGramDictionary object</returns>
public static NGramDictionary DeserializeFrom(string str)
{
string[] lines = str.Split('\n');
int minNGram = Int32.Parse(lines[0].Split('\t')[0]);
int maxNGram = Int32.Parse(lines[0].Split('\t')[1]);
IDictionary<NGram, int> nGrams = new Dictionary<NGram, int>();
var extractor = new NGramExtractor(minNGram, maxNGram);
foreach (string line in lines.Skip(1))
{
string[] row = line.Split('\t');
var nGram = new NGram(row[0].Split(null));
int freq = Int32.Parse(row[1]);
if (!nGrams.ContainsKey(nGram))
{
nGrams.Add(nGram, freq);
}
}
return new NGramDictionary(extractor, nGrams);
}
public void TestEquals()
{
var trigram1 = new NGram(new List<string> {"one", "two", "three"});
var trigram2 = new NGram(new List<string> {"one", "two", "three"});
Assert.AreEqual(trigram1, trigram2);
Assert.AreEqual(trigram1.GetHashCode(), trigram2.GetHashCode());
trigram1 = new NGram(new List<string> {"two", "one", "three"});
trigram2 = new NGram(new List<string> {"one", "two", "three"});
Assert.AreNotEqual(trigram1, trigram2);
Assert.AreNotEqual(trigram1.GetHashCode(), trigram2.GetHashCode());
trigram1 = new NGram("one", "two", "three");
trigram2 = new NGram("one", "two", "three");
Assert.AreEqual(trigram1, trigram2);
Assert.AreEqual(trigram1.GetHashCode(), trigram2.GetHashCode());
trigram1 = new NGram("two", "one", "three");
trigram2 = new NGram("one", "two", "three");
Assert.AreNotEqual(trigram1, trigram2);
Assert.AreNotEqual(trigram1.GetHashCode(), trigram2.GetHashCode());
}
public double GetMLE(NGram denominatorNGram, NGram nominatorNGram)
{
int nom = nGramDictionary.GetFrequency(nominatorNGram);
int denom = nGramDictionary.GetFrequency(denominatorNGram);
if (denom == 0)
{
return 0;
}
return nom/(double) denom;
}
/// <summary>
/// returns requency of the n-gram
/// </summary>
/// <param name="nGram"></param>
/// <returns></returns>
public int GetFrequency(NGram nGram)
{
if (nGrams.ContainsKey(nGram))
{
return nGrams[nGram];
}
return 0;
}
/// <summary>
/// returns frequency of the n-gram which consists of nGramTokens
/// </summary>
/// <param name="nGramTokens">Tokens of the n-gram</param>
/// <returns></returns>
public int GetFrequency(params string[] nGramTokens)
{
Validate(nGramTokens);
var nGram = new NGram(nGramTokens);
return GetFrequency(nGram);
}
private bool Equals(NGram other)
{
return Tokens.SequenceEqual(other.Tokens);
}
public double GetUnigramMLE(NGram nGram)
{
return nGramDictionary.GetFrequency(nGram)/(double) tokenCount;
}
