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+// The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
+/*
+ This is an example illustrating the use of the krls object
+ from the dlib C++ Library.
+
+ The krls object allows you to perform online regression. This
+ example will train an instance of it on the sinc function.
+
+*/
+
+#include <iostream>
+#include <vector>
+
+#include <dlib/svm.h>
+
+using namespace std;
+using namespace dlib;
+
+// Here is the sinc function we will be trying to learn with the krls
+// object.
+double sinc(double x)
+{
+ if (x == 0)
+ return 1;
+ return sin(x)/x;
+}
+
+int main()
+{
+ // Here we declare that our samples will be 1 dimensional column vectors. In general,
+ // you can use N dimensional vectors as inputs to the krls object. But here we only
+ // have 1 dimension to make the example simple. (Note that if you don't know the
+ // dimensionality of your vectors at compile time you can change the first number to
+ // a 0 and then set the size at runtime)
+ typedef matrix<double,1,1> sample_type;
+
+ // Now we are making a typedef for the kind of kernel we want to use. I picked the
+ // radial basis kernel because it only has one parameter and generally gives good
+ // results without much fiddling.
+ typedef radial_basis_kernel<sample_type> kernel_type;
+
+ // Here we declare an instance of the krls object. The first argument to the constructor
+ // is the kernel we wish to use. The second is a parameter that determines the numerical
+ // accuracy with which the object will perform part of the regression algorithm. Generally
+ // smaller values give better results but cause the algorithm to run slower. You just have
+ // to play with it to decide what balance of speed and accuracy is right for your problem.
+ // Here we have set it to 0.001.
+ krls<kernel_type> test(kernel_type(0.1),0.001);
+
+ // now we train our object on a few samples of the sinc function.
+ sample_type m;
+ for (double x = -10; x <= 4; x += 1)
+ {
+ m(0) = x;
+ test.train(m, sinc(x));
+ }
+
+ // now we output the value of the sinc function for a few test points as well as the
+ // value predicted by krls object.
+ m(0) = 2.5; cout << sinc(m(0)) << " " << test(m) << endl;
+ m(0) = 0.1; cout << sinc(m(0)) << " " << test(m) << endl;
+ m(0) = -4; cout << sinc(m(0)) << " " << test(m) << endl;
+ m(0) = 5.0; cout << sinc(m(0)) << " " << test(m) << endl;
+
+ // The output is as follows:
+ // 0.239389 0.239362
+ // 0.998334 0.998333
+ // -0.189201 -0.189201
+ // -0.191785 -0.197267
+
+
+ // The first column is the true value of the sinc function and the second
+ // column is the output from the krls estimate.
+
+
+
+
+
+ // Another thing that is worth knowing is that just about everything in dlib is serializable.
+ // So for example, you can save the test object to disk and recall it later like so:
+ serialize("saved_krls_object.dat") << test;
+
+ // Now let's open that file back up and load the krls object it contains.
+ deserialize("saved_krls_object.dat") >> test;
+
+ // If you don't want to save the whole krls object (it might be a bit large)
+ // you can save just the decision function it has learned so far. You can get
+ // the decision function out of it by calling test.get_decision_function() and
+ // then you can serialize that object instead. E.g.
+ decision_function<kernel_type> funct = test.get_decision_function();
+ serialize("saved_krls_function.dat") << funct;
+}
+
+