/// <summary>
/// Calculates the entropy of <paramref name="input" />.
/// </summary>
/// <param name="input"></param>
/// <param name="logarithmBase"></param>
/// <returns></returns>
public static double Analyze(string input, double logarithmBase = 2)
{
if (input == null)
{
throw new ArgumentNullException(nameof(input));
}
return(-(
from kv in FrequencyAnalysis.Analyze(input)
let occurrence = kv.Value
let probability = (double)occurrence / input.Length
select probability * Math.Log(probability, logarithmBase)
).Sum());
}
/// <summary>
/// Return 1 when the substring is found in the candidate, 0 if not.
/// </summary>
/// <param name="speculativePlaintext"></param>
/// <returns></returns>
public double Classify(string speculativePlaintext)
{
return(FrequencyAnalysis.Compare(_relativeFrequencies, Analyze(speculativePlaintext).AsRelativeFrequencies()));
}