Question

我正在使用accord.net。以下示例工作正常，但我想制作Multi类分类器。我尝试使用MulticlassSupportVectorMachine（）函数，但它为动态时间扭曲类内核训练数据时出现0.6错误，这对于某些输入没有给出正确的输出。

    // Suppose you have sequences of multivariate observations, and that
// those sequences could be of arbitrary length. On the other hand, 
// each observation have a fixed, delimited number of dimensions.

// In this example, we have sequences of 3-dimensional observations. 
// Each sequence can have an arbitrary length, but each observation
// will always have length 3:   
 double[][][] sequences ={
  new double[][] // first sequence
{
    new double[] { 1, 1, 1 }, // first observation of the first sequence
    new double[] { 1, 2, 1 }, // second observation of the first sequence
    new double[] { 1, 4, 2 }, // third observation of the first sequence
    new double[] { 2, 2, 2 }, // fourth observation of the first sequence
},

new double[][] // second sequence (note that this sequence has a different length)
{
    new double[] { 1, 1, 1 }, // first observation of the second sequence
    new double[] { 1, 5, 6 }, // second observation of the second sequence
    new double[] { 2, 7, 1 }, // third observation of the second sequence
},

new double[][] // third sequence 
{
    new double[] { 8, 2, 1 }, // first observation of the third sequence
},

new double[][] // fourth sequence 
{
    new double[] { 8, 2, 5 }, // first observation of the fourth sequence
    new double[] { 1, 5, 4 }, // second observation of the fourth sequence
}
};
// Now, we will also have different class labels associated which each 
// sequence. We will assign -1 to sequences whose observations start 
// with { 1, 1, 1 } and +1 to those that do not:

int[] outputs =
{
  -1,-1,  // First two sequences are of class -1 (those start with {1,1,1})
    1, 1,  // Last two sequences are of class +1  (don't start with {1,1,1})
};

// At this point, we will have to "flat" out the input sequences from             double[][][]
    // to a double[][] so they can be properly understood by the SVMs. The      problem is 
// that, normally, SVMs usually expect the data to be comprised of fixed-length 
// input vectors and associated class labels. But in this case, we will be feeding
// them arbitrary-length sequences of input vectors and class labels associated with
// each sequence, instead of each vector.

double[][] inputs = new double[sequences.Length][];
for (int i = 0; i < sequences.Length; i++)
inputs[i] = Matrix.Concatenate(sequences[i]);


// Now we have to setup the Dynamic Time Warping kernel. We will have to
// inform the length of the fixed-length observations contained in each
// arbitrary-length sequence:
// 
DynamicTimeWarping kernel = new DynamicTimeWarping(length: 3);

// Now we can create the machine. When using variable-length
/    / kernels, we will need to pass zero as the input length:
var svm = new KernelSupportVectorMachine(kernel, inputs: 0);


// Create the Sequential Minimal Optimization learning algorithm
var smo = new SequentialMinimalOptimization(svm, inputs, outputs)
{
Complexity = 1.5
};

// And start learning it!
double error = smo.Run(); // error will be 0.0


// At this point, we should have obtained an useful machine. Let's
// see if it can understand a few examples it hasn't seem before:

double[][] a = 
{ 
new double[] { 1, 1, 1 },
new double[] { 7, 2, 5 },
new double[] { 2, 5, 1 },
};

double[][] b =
{
new double[] { 7, 5, 2 },
new double[] { 4, 2, 5 },
new double[] { 1, 1, 1 },
};

// Following the aforementioned logic, sequence (a) should be
// classified as -1, and sequence (b) should be classified as +1.

int resultA = System.Math.Sign(svm.Compute(Matrix.Concatenate(a))); // -1
int resultB = System.Math.Sign(svm.Compute(Matrix.Concatenate(b))); // +1

我需要帮助来使用MulticlassSupportVectorMachine（）来实现Multi class SVM分类器，它可以训练机器输入两种以上的类型，并为每种输入类型提供输出标签。 P.S：如果MulticlassSupportVectorMachine（）函数不支持动态时间扭曲内核。请告诉我如何在上面的动态时间扭曲内核中使用一对一的多类svm技术，并使用一对一技术制作多分类器。非常感谢您的帮助。在此先感谢。

Answer 1

此代码适用于我

var smo = new MulticlassSupportVectorLearning<DynamicTimeWarping, double[][]>()
            {
                // Set the parameters of the kernel
                Kernel = new DynamicTimeWarping(alpha: 1, degree: 1)
            };
            // And use it to learn a machine!
            var svm = smo.Learn(words, labels);
            // Create the multi-class learning algorithm for the machine
            var calibration = new MulticlassSupportVectorLearning<DynamicTimeWarping, double[][]>()
            {
                Model = svm, // We will start with an existing machine

                // Configure the learning algorithm to use SMO to train the
                //  underlying SVMs in each of the binary class subproblems.
                Learner = (param) => new ProbabilisticOutputCalibration<DynamicTimeWarping, double[][]>()
                {
                    Model = param.Model // Start with an existing machine
                }
            };
            // Configure parallel execution options
            calibration.ParallelOptions.MaxDegreeOfParallelism = 1;
            // Learn a machine
            calibration.Learn(words, labels);
            // Obtain class predictions for each sample
            int[] predicted = svm.Decide(words);
            int[] expected = new int[words.Length];


            double correct = 0;
            for (int i = 0; i < words.Length; i++)
            {
                expected[i] = labels[i];
                predicted[i] = svm.Decide(words[i]);
                if (svm.Decide(words[i]) == labels[i])
                {
                    correct++;
                }

            }
            string Accurecy = "SMO Accurecy = " + (correct / predicted.Length).ToString() + Environment.NewLine; // ori

我想使用动态时间扭曲内核制作多类SVM

1 个答案: