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Updated the examples to make more sense with respect to the updated kcentroid.

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Davis King 2009-03-16 03:26:54 +00:00
parent 43a7f59054
commit 7404ceb822
3 changed files with 37 additions and 46 deletions
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67
examples/kcentroid_ex.cpp
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@ -7,7 +7,8 @@
computes the centroid (i.e. average) of a set of points. The interesting
thing about dlib::kcentroid is that it does so in a kernel induced feature
space. This means that you can use it as a non-linear one-class classifier.
So you might use it to perform online novelty detection.
So you might use it to perform online novelty detection (although, it has
other uses, see the svm_pegasos or kkmeans examples for example).
This example will train an instance of it on points from the sinc function.
@ -43,27 +44,15 @@ int main()
// results without much fiddling.
typedef radial_basis_kernel<sample_type> kernel_type;
// Here we declare an instance of the kcentroid 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 learning 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 0.01.
//
// Also, since we are using the radial basis kernel we have to pick the RBF width parameter.
// Here we have it set to 0.1. But in general, a reasonable way of picking this value is
// to start with some initial guess and to just run the algorithm. Then print out
// test.dictionary_size() to see how many support vectors the kcentroid object is using.
// And a good rule of thumb is that you should have somewhere in the range of 10-100
// support vectors. So if you aren't in that range then you can change the RBF parameter.
// Making it smaller will decrease the dictionary size and making it bigger will increase
// the dictionary size.
//
// So what I often do is I set the kcentroid's second parameter to 0.01 or 0.001. Then
// I find an RBF kernel parameter that gives me the number of support vectors that I
// feel is appropriate for the problem I'm trying to solve. Again, this just comes down
// to playing with it and getting a feel for how things work.
kcentroid<kernel_type> test(kernel_type(0.1),0.01);
// Here we declare an instance of the kcentroid object. The kcentroid has 3 parameters
// you need to set. 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 the centroid estimation. Generally, smaller values
// give better results but cause the algorithm to attempt to use more support vectors
// (and thus run slower and use more memory). The third argument, however, is the
// maximum number of support vectors a kcentroid is allowed to use. So you can use
// it to control the runtime complexity.
kcentroid<kernel_type> test(kernel_type(0.1),0.01, 15);
// now we train our object on a few samples of the sinc function.
@ -105,25 +94,31 @@ int main()
m(0) = -1.5; m(1) = sinc(m(0))+0.9; cout << " " << test(m) << " is " << rs.scale(test(m)) << " standard deviations from sinc." << endl;
m(0) = -0.5; m(1) = sinc(m(0))+1; cout << " " << test(m) << " is " << rs.scale(test(m)) << " standard deviations from sinc." << endl;
cout << "\nmean: " << rs.mean() << endl;
cout << "standard deviation: " << sqrt(rs.variance()) << endl;
// The output is as follows:
/*
Points that are on the sinc function:
0.869861
0.869861
0.873182
0.872628
0.870352
0.869861
0.872628
0.869913
0.869913
0.873408
0.872807
0.870432
0.869913
0.872807
Points that are NOT on the sinc function:
1.06306 is 125.137 standard deviations from sinc.
1.0215 is 98.0313 standard deviations from sinc.
0.92136 is 32.717 standard deviations from sinc.
0.918282 is 30.7096 standard deviations from sinc.
0.930931 is 38.9595 standard deviations from sinc.
0.897916 is 17.4264 standard deviations from sinc.
0.913855 is 27.822 standard deviations from sinc.
1.06366 is 119.65 standard deviations from sinc.
1.02212 is 93.8106 standard deviations from sinc.
0.921382 is 31.1458 standard deviations from sinc.
0.918439 is 29.3147 standard deviations from sinc.
0.931428 is 37.3949 standard deviations from sinc.
0.898018 is 16.6121 standard deviations from sinc.
0.914425 is 26.8183 standard deviations from sinc.
mean: 0.871313
standard deviation: 0.00160756
*/
// So we can see that in this example the kcentroid object correctly indicates that

8
examples/kkmeans_ex.cpp
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@ -42,17 +42,15 @@ int main()
// Here we declare an instance of the kcentroid object. It is the object used to
// represent each of the centers used for clustering. The kcentroid has 4 parameters
// represent each of the centers used for clustering. The kcentroid has 3 parameters
// you need to set. 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 learning algorithm. Generally, smaller values
// give better results but cause the algorithm to attempt to use more support vectors
// (and thus run slower and use more memory). The third argument, however, is the
// maximum number of support vectors a kcentroid is allowed to use. So you can use
// it to control the complexity. Finally, the last argument should always be set to
// false when using a kcentroid for clustering (see the kcentroid docs for details on
// this parameter).
kcentroid<kernel_type> kc(kernel_type(0.1),0.01, 8, false);
// it to control the runtime complexity.
kcentroid<kernel_type> kc(kernel_type(0.1),0.01, 8);
// Now we make an instance of the kkmeans object and tell it to use kcentroid objects
// that are configured with the parameters from the kc object we defined above.

8
examples/rank_features_ex.cpp
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@ -98,17 +98,15 @@ int main()
typedef radial_basis_kernel<sample_type> kernel_type;
// Here we declare an instance of the kcentroid object. It is used by rank_features()
// two represent the centroids of the two classes. The kcentroid has 4 parameters
// two represent the centroids of the two classes. The kcentroid has 3 parameters
// you need to set. 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 ranking algorithm. Generally, smaller values
// give better results but cause the algorithm to attempt to use more support vectors
// (and thus run slower and use more memory). The third argument, however, is the
// maximum number of support vectors a kcentroid is allowed to use. So you can use
// it to control the complexity. Finally, the last argument should always be set to
// false when using a kcentroid for ranking (see the kcentroid docs for details on
// this parameter).
kcentroid<kernel_type> kc(kernel_type(0.05), 0.001, 25, false);
// it to control the runtime complexity.
kcentroid<kernel_type> kc(kernel_type(0.05), 0.001, 25);
// And finally we get to the feature ranking. Here we call rank_features() with the kcentroid we just made,
// the samples and labels we made above, and the number of features we want it to rank.