public double GetProbability(TItem item, Ngram <TItem> context)
{
FrequencyDistribution <TItem> freqDist = _cfd[context];
if (freqDist.ObservedSamples.Count == 0)
{
return(0);
}
double numer = freqDist[item] + (freqDist.ObservedSamples.Count * (_lowerOrderModel == null ? 1.0 / freqDist.ObservedSamples.Count
: _lowerOrderModel.GetProbability(item, context.SkipFirst(_dir))));
double denom = freqDist.SampleOutcomeCount + freqDist.ObservedSamples.Count;
return(numer / denom);
}
public double GetProbability(TItem item, Ngram <TItem> context)
{
FrequencyDistribution <TItem> freqDist = _cfd[context];
if (freqDist.ObservedSamples.Count == 0)
{
return(0);
}
if (context.Length == 0)
{
return((double)freqDist[item] / freqDist.SampleOutcomeCount);
}
int count = freqDist[item];
Tuple <int, int, int> bigN = _bigNs[context];
double gamma = ((_discount1 * bigN.Item1) + (_discount2 * bigN.Item2) + (_discount3 * bigN.Item3)) / freqDist.SampleOutcomeCount;
double d = 0;
if (count == 1)
{
d = _discount1;
}
else if (count == 2)
{
d = _discount2;
}
else if (count > 2)
{
d = _discount3;
}
double prob = (count - d) / freqDist.SampleOutcomeCount;
return(prob + (gamma * _lowerOrderModel.GetProbability(item, context.SkipFirst(_dir))));
}