public void LearnTest3()
{
Accord.Math.Tools.SetupGenerator(0);
// We will try to create a Hidden Markov Model which
// can detect if a given sequence starts with a zero
// and has any number of ones after that.
//
int[][] sequences = new int[][]
{
new int[] { 0,1,1,1,1,0,1,1,1,1 },
new int[] { 0,1,1,1,0,1,1,1,1,1 },
new int[] { 0,1,1,1,1,1,1,1,1,1 },
new int[] { 0,1,1,1,1,1 },
new int[] { 0,1,1,1,1,1,1 },
new int[] { 0,1,1,1,1,1,1,1,1,1 },
new int[] { 0,1,1,1,1,1,1,1,1,1 },
};
// Creates a new Hidden Markov Model with 3 states for
// an output alphabet of two characters (zero and one)
//
HiddenMarkovModel hmm = new HiddenMarkovModel(new Forward(3), 2);
// Try to fit the model to the data until the difference in
// the average log-likelihood changes only by as little as 0.0001
//
var teacher = new ViterbiLearning(hmm) { Tolerance = 0.0001, Iterations = 0 };
//
double ll = teacher.Run(sequences);
// Calculate the probability that the given
// sequences originated from the model
//
double l1; hmm.Decode(new int[] { 0, 1 }, out l1); // 0.5394
double l2; hmm.Decode(new int[] { 0, 1, 1, 1 }, out l2); // 0.4485
// Sequences which do not start with zero have much lesser probability.
double l3; hmm.Decode(new int[] { 1, 1 }, out l3); // 0.0864
double l4; hmm.Decode(new int[] { 1, 0, 0, 0 }, out l4); // 0.0004
// Sequences which contains few errors have higher probability
// than the ones which do not start with zero. This shows some
// of the temporal elasticity and error tolerance of the HMMs.
//
double l5; hmm.Decode(new int[] { 0, 1, 0, 1, 1, 1, 1, 1, 1 }, out l5); // 0.0154
double l6; hmm.Decode(new int[] { 0, 1, 1, 1, 1, 1, 1, 0, 1 }, out l6); // 0.0154
ll = System.Math.Exp(ll);
l1 = System.Math.Exp(l1);
l2 = System.Math.Exp(l2);
l3 = System.Math.Exp(l3);
l4 = System.Math.Exp(l4);
l5 = System.Math.Exp(l5);
l6 = System.Math.Exp(l6);
Assert.AreEqual(1.754393540912413, ll, 1e-6);
Assert.AreEqual(0.53946360153256712, l1, 1e-6);
Assert.AreEqual(0.44850249229903377, l2, 1e-6);
Assert.AreEqual(0.08646414524833077, l3, 1e-6);
Assert.AreEqual(0.00041152263374485, l4, 1e-6);
Assert.AreEqual(0.01541807695931400, l5, 1e-6);
Assert.AreEqual(0.01541807695931400, l6, 1e-6);
Assert.IsTrue(l1 > l3 && l1 > l4);
Assert.IsTrue(l2 > l3 && l2 > l4);
}
