我正致力于手势识别项目。我的数据集由4种不同的手势组成,每个手势集包含大约70个图像。我为每个图像提取了4个特征。我正在尝试使用Accord.Net来实现HMM,我知道我将需要4个HMM,每个手势一个,但我不知道如何构建用于学习/训练的特征向量序列相。有谁知道如何解决它?
这是序列的简单代码:
double[][] sequences = new double[][]
{
new double[] { 0,1,2,3,4 }, // This is the first sequence with label = 0
new double[] { 4,3,2,1,0 }, // This is the second sequence with label = 1
};
// Labels for the sequences
int[] labels = { 0, 1 };
答案 0 :(得分:3)
你是对的,每个手势都需要一个HMM。但是,如果您使用HiddenMarkovClassifier类(它是在您尝试检测的每个类之后创建的多个HMM的包装器),框架已经可以为您提供此构造。
如果每个图像有4个要素,则需要假设能够对多变量要素建模的概率分布。一个简单的选择是假设您的功能彼此独立,并且每个功能都遵循正态分布。
因此,您可以使用以下示例代码来创建模型。它假设您的数据库只有两个训练序列,但实际上你必须有许多。
double[][][] sequences = new double[][][]
{
new double[][] // This is the first sequence with label = 0
{
new double[] { 0, 1, 2, 1 }, // <-- this is the 4-features feature vector for
new double[] { 1, 2, 5, 2 }, // the first image of the first sequence
new double[] { 2, 3, 2, 5 },
new double[] { 3, 4, 1, 1 },
new double[] { 4, 5, 2, 2 },
},
new double[][] // This is the second sequence with label = 1
{
new double[] { 4, 3, 4, 1 }, // <-- this is the 4-features feature vector for
new double[] { 3, 2, 2, 2 }, // the first image of the second sequence
new double[] { 2, 1, 1, 1 },
new double[] { 1, 0, 2, 2 },
new double[] { 0, -1, 1, 2 },
}
};
// Labels for the sequences
int[] labels = { 0, 1 };
上面的代码显示了如何设置学习数据库。现在,一旦设置完毕,就可以为4个正常特征创建一个隐藏的马尔可夫分类器(假设正态分布之间的独立性)为
// Create one base Normal distribution to be replicated accross the states
var initialDensity = new MultivariateNormalDistribution(4); // we have 4 features
// Creates a sequence classifier containing 2 hidden Markov Models with 2 states
// and an underlying multivariate mixture of Normal distributions as density.
var classifier = new HiddenMarkovClassifier<MultivariateNormalDistribution>(
classes: 2, topology: new Forward(2), initial: initialDensity);
// Configure the learning algorithms to train the sequence classifier
var teacher = new HiddenMarkovClassifierLearning<MultivariateNormalDistribution>(
classifier,
// Train each model until the log-likelihood changes less than 0.0001
modelIndex => new BaumWelchLearning<MultivariateNormalDistribution>(
classifier.Models[modelIndex])
{
Tolerance = 0.0001,
Iterations = 0,
FittingOptions = new NormalOptions()
{
Diagonal = true, // only diagonal covariance matrices
Regularization = 1e-5 // avoid non-positive definite errors
}
// PS: Setting diagonal = true means the features will be
// assumed independent of each other. This can also be
// achieved by using an Independent<NormalDistribution>
// instead of a diagonal multivariate Normal distribution
}
);
最后,我们可以训练模型并在学习数据上测试其输出:
// Train the sequence classifier using the algorithm
double logLikelihood = teacher.Run(sequences, labels);
// Calculate the probability that the given
// sequences originated from the model
double likelihood, likelihood2;
// Try to classify the 1st sequence (output should be 0)
int c1 = classifier.Compute(sequences[0], out likelihood);
// Try to classify the 2nd sequence (output should be 1)
int c2 = classifier.Compute(sequences[1], out likelihood2);