public void ApplyTest2()
{
// Suppose we have a data table relating the age of
// a person and its categorical classification, as
// in "child", "adult" or "elder".
// The Codification filter is able to extract those
// string labels and transform them into discrete
// symbols, assigning integer labels to each of them
// such as "child" = 0, "adult" = 1, and "elder" = 3.
// Create the aforementioned sample table
DataTable table = new DataTable("Sample data");
table.Columns.Add("Age", typeof(int));
table.Columns.Add("Label", typeof(string));
// age label
table.Rows.Add(10, "child");
table.Rows.Add(07, "child");
table.Rows.Add(04, "child");
table.Rows.Add(21, "adult");
table.Rows.Add(27, "adult");
table.Rows.Add(12, "child");
table.Rows.Add(79, "elder");
table.Rows.Add(40, "adult");
table.Rows.Add(30, "adult");
// Now, let's say we need to translate those text labels
// into integer symbols. Let's use a Codification filter:
Codification codebook = new Codification(table);
// After that, we can use the codebook to "translate"
// the text labels into discrete symbols, such as:
int a = codebook.Translate("Label", "child"); // returns 0
int b = codebook.Translate("Label", "adult"); // returns 1
int c = codebook.Translate("Label", "elder"); // returns 2
// We can also do the reverse:
string labela = codebook.Translate("Label", 0); // returns "child"
string labelb = codebook.Translate("Label", 1); // returns "adult"
string labelc = codebook.Translate("Label", 2); // returns "elder"
// We can also process an entire data table at once:
DataTable result = codebook.Apply(table);
// The resulting table can be transformed to jagged array:
double[][] matrix = Matrix.ToArray(result);
// and the resulting matrix will be given by
string str = matrix.ToString(CSharpJaggedMatrixFormatProvider.InvariantCulture);
// str == new double[][]
// {
// new double[] { 10, 0 },
// new double[] { 7, 0 },
// new double[] { 4, 0 },
// new double[] { 21, 1 },
// new double[] { 27, 1 },
// new double[] { 12, 0 },
// new double[] { 79, 2 },
// new double[] { 40, 1 },
// new double[] { 30, 1 }
// };
// Now we will be able to feed this matrix to any machine learning
// algorithm without having to worry about text labels in our data:
int classes = codebook["Label"].Symbols; // 3 classes (child, adult, elder)
// Use the first column as input variables,
// and the second column as outputs classes
//
double[][] inputs = matrix.GetColumns(new[] { 0 });
int[] outputs = matrix.GetColumn(1).ToInt32();
// Create a multi-class SVM for 1 input (Age) and 3 classes (Label)
var machine = new MulticlassSupportVectorMachine(inputs: 1, classes: classes);
// Create a Multi-class learning algorithm for the machine
var teacher = new MulticlassSupportVectorLearning(machine, inputs, outputs);
// Configure the learning algorithm to use SMO to train the
// underlying SVMs in each of the binary class subproblems.
teacher.Algorithm = (svm, classInputs, classOutputs, i, j) =>
{
return new SequentialMinimalOptimization(svm, classInputs, classOutputs)
{
Complexity = 1
};
};
// Run the learning algorithm
double error = teacher.Run();
// After we have learned the machine, we can use it to classify
// new data points, and use the codebook to translate the machine
// outputs to the original text labels:
string result1 = codebook.Translate("Label", machine.Compute(10)); // child
string result2 = codebook.Translate("Label", machine.Compute(40)); // adult
string result3 = codebook.Translate("Label", machine.Compute(70)); // elder
Assert.AreEqual(0, a);
Assert.AreEqual(1, b);
Assert.AreEqual(2, c);
Assert.AreEqual("child", labela);
Assert.AreEqual("adult", labelb);
Assert.AreEqual("elder", labelc);
Assert.AreEqual("child", result1);
Assert.AreEqual("adult", result2);
Assert.AreEqual("elder", result3);
}
