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Commit 46bb6dc8 authored by Davis King's avatar Davis King
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Added code showing how to get the individual decision functions out of a 

multiclass decision function object.
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examples/multiclass_classification_ex.cpp
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......@@ -42,116 +42,145 @@ void generate_data (
int main()
{
std::vector<sample_type> samples;
std::vector<double> labels;
// First, get our labeled set of training data
generate_data(samples, labels);
cout << "samples.size(): "<< samples.size() << endl;
// The main object in this example program is the one_vs_one_trainer. It is essentially
// a container class for regular binary classifier trainer objects. In particular, it
// uses the any_trainer object to store any kind of trainer object that implements a
// .train(samples,labels) function which returns some kind of learned decision function.
// It uses these binary classifiers to construct a voting multiclass classifier. If
// there are N classes then it trains N*(N-1)/2 binary classifiers, one for each pair of
// labels, which then vote on the label of a sample.
//
// In this example program we will work with a one_vs_one_trainer object which stores any
// kind of trainer that uses our sample_type samples.
typedef one_vs_one_trainer<any_trainer<sample_type> > ovo_trainer;
// Finally, make the one_vs_one_trainer.
ovo_trainer trainer;
// Next, we will make two different binary classification trainer objects. One
// which uses kernel ridge regression and RBF kernels and another which uses a
// support vector machine and polynomial kernels. The particular details don't matter.
// The point of this part of the example is that you can use any kind of trainer object
// with the one_vs_one_trainer.
typedef polynomial_kernel<sample_type> poly_kernel;
typedef radial_basis_kernel<sample_type> rbf_kernel;
// make the binary trainers and set some parameters
krr_trainer<rbf_kernel> rbf_trainer;
svm_nu_trainer<poly_kernel> poly_trainer;
poly_trainer.set_kernel(poly_kernel(0.1, 1, 2));
rbf_trainer.set_kernel(rbf_kernel(0.1));
// Now tell the one_vs_one_trainer that, by default, it should use the rbf_trainer
// to solve the individual binary classification subproblems.
trainer.set_trainer(rbf_trainer);
// We can also get more specific. Here we tell the one_vs_one_trainer to use the
// poly_trainer to solve the class 1 vs class 2 subproblem. All the others will
// still be solved with the rbf_trainer.
trainer.set_trainer(poly_trainer, 1, 2);
// Now lets do 5-fold cross-validation using the one_vs_one_trainer we just setup.
// As an aside, always shuffle the order of the samples before doing cross validation.
// For a discussion of why this is a good idea see the svm_ex.cpp example.
randomize_samples(samples, labels);
cout << "cross validation: \n" << cross_validate_multiclass_trainer(trainer, samples, labels, 5) << endl;
// The output is shown below. It is the confusion matrix which describes the results. Each row
// corresponds to a class of data and each column to a prediction. Reading from top to bottom,
// the rows correspond to the class labels if the labels have been listed in sorted order. So the
// top row corresponds to class 1, the middle row to class 2, and the bottom row to class 3. The
// columns are organized similarly, with the left most column showing how many samples were predicted
// as members of class 1.
//
// So in the results below we can see that, for the class 1 samples, 60 of them were correctly predicted
// to be members of class 1 and 0 were incorrectly classified. Similarly, the other two classes of data
// are perfectly classified.
/*
cross validation:
60 0 0
0 70 0
0 0 80
*/
// Next, if you wanted to obtain the decision rule learned by a one_vs_one_trainer you
// would store it into a one_vs_one_decision_function.
one_vs_one_decision_function<ovo_trainer> df = trainer.train(samples, labels);
cout << "predicted label: "<< df(samples[0]) << ", true label: "<< labels[0] << endl;
cout << "predicted label: "<< df(samples[90]) << ", true label: "<< labels[90] << endl;
// The output is:
/*
predicted label: 2, true label: 2
predicted label: 1, true label: 1
*/
// Finally, if you want to save a one_vs_one_decision_function to disk, you can do
// so. However, you must declare what kind of decision functions it contains.
one_vs_one_decision_function<ovo_trainer,
decision_function<poly_kernel>, // This is the output of the poly_trainer
decision_function<rbf_kernel> // This is the output of the rbf_trainer
try
{
std::vector<sample_type> samples;
std::vector<double> labels;
// First, get our labeled set of training data
generate_data(samples, labels);
cout << "samples.size(): "<< samples.size() << endl;
// The main object in this example program is the one_vs_one_trainer. It is essentially
// a container class for regular binary classifier trainer objects. In particular, it
// uses the any_trainer object to store any kind of trainer object that implements a
// .train(samples,labels) function which returns some kind of learned decision function.
// It uses these binary classifiers to construct a voting multiclass classifier. If
// there are N classes then it trains N*(N-1)/2 binary classifiers, one for each pair of
// labels, which then vote on the label of a sample.
//
// In this example program we will work with a one_vs_one_trainer object which stores any
// kind of trainer that uses our sample_type samples.
typedef one_vs_one_trainer<any_trainer<sample_type> > ovo_trainer;
// Finally, make the one_vs_one_trainer.
ovo_trainer trainer;
// Next, we will make two different binary classification trainer objects. One
// which uses kernel ridge regression and RBF kernels and another which uses a
// support vector machine and polynomial kernels. The particular details don't matter.
// The point of this part of the example is that you can use any kind of trainer object
// with the one_vs_one_trainer.
typedef polynomial_kernel<sample_type> poly_kernel;
typedef radial_basis_kernel<sample_type> rbf_kernel;
// make the binary trainers and set some parameters
krr_trainer<rbf_kernel> rbf_trainer;
svm_nu_trainer<poly_kernel> poly_trainer;
poly_trainer.set_kernel(poly_kernel(0.1, 1, 2));
rbf_trainer.set_kernel(rbf_kernel(0.1));
// Now tell the one_vs_one_trainer that, by default, it should use the rbf_trainer
// to solve the individual binary classification subproblems.
trainer.set_trainer(rbf_trainer);
// We can also get more specific. Here we tell the one_vs_one_trainer to use the
// poly_trainer to solve the class 1 vs class 2 subproblem. All the others will
// still be solved with the rbf_trainer.
trainer.set_trainer(poly_trainer, 1, 2);
// Now lets do 5-fold cross-validation using the one_vs_one_trainer we just setup.
// As an aside, always shuffle the order of the samples before doing cross validation.
// For a discussion of why this is a good idea see the svm_ex.cpp example.
randomize_samples(samples, labels);
cout << "cross validation: \n" << cross_validate_multiclass_trainer(trainer, samples, labels, 5) << endl;
// The output is shown below. It is the confusion matrix which describes the results. Each row
// corresponds to a class of data and each column to a prediction. Reading from top to bottom,
// the rows correspond to the class labels if the labels have been listed in sorted order. So the
// top row corresponds to class 1, the middle row to class 2, and the bottom row to class 3. The
// columns are organized similarly, with the left most column showing how many samples were predicted
// as members of class 1.
//
// So in the results below we can see that, for the class 1 samples, 60 of them were correctly predicted
// to be members of class 1 and 0 were incorrectly classified. Similarly, the other two classes of data
// are perfectly classified.
/*
cross validation:
60 0 0
0 70 0
0 0 80
*/
// Next, if you wanted to obtain the decision rule learned by a one_vs_one_trainer you
// would store it into a one_vs_one_decision_function.
one_vs_one_decision_function<ovo_trainer> df = trainer.train(samples, labels);
cout << "predicted label: "<< df(samples[0]) << ", true label: "<< labels[0] << endl;
cout << "predicted label: "<< df(samples[90]) << ", true label: "<< labels[90] << endl;
// The output is:
/*
predicted label: 2, true label: 2
predicted label: 1, true label: 1
*/
// If you want to save a one_vs_one_decision_function to disk, you can do
// so. However, you must declare what kind of decision functions it contains.
one_vs_one_decision_function<ovo_trainer,
decision_function<poly_kernel>, // This is the output of the poly_trainer
decision_function<rbf_kernel> // This is the output of the rbf_trainer
> df2, df3;
// Put df into df2 and then save df2 to disk. Note that we could have also said
// df2 = trainer.train(samples, labels); But doing it this way avoids retraining.
df2 = df;
ofstream fout("df.dat", ios::binary);
serialize(df2, fout);
fout.close();
// Put df into df2 and then save df2 to disk. Note that we could have also said
// df2 = trainer.train(samples, labels); But doing it this way avoids retraining.
df2 = df;
ofstream fout("df.dat", ios::binary);
serialize(df2, fout);
fout.close();
// load the function back in from disk and store it in df3.
ifstream fin("df.dat", ios::binary);
deserialize(df3, fin);
// Test df3 to see that this worked.
cout << endl;
cout << "predicted label: "<< df3(samples[0]) << ", true label: "<< labels[0] << endl;
cout << "predicted label: "<< df3(samples[90]) << ", true label: "<< labels[90] << endl;
// Test df3 on the samples and labels and print the confusion matrix.
cout << "test deserialized function: \n" << test_multiclass_decision_function(df3, samples, labels) << endl;
// load the function back in from disk and store it in df3.
ifstream fin("df.dat", ios::binary);
deserialize(df3, fin);
// Test df3 to see that this worked.
cout << endl;
cout << "predicted label: "<< df3(samples[0]) << ", true label: "<< labels[0] << endl;
cout << "predicted label: "<< df3(samples[90]) << ", true label: "<< labels[90] << endl;
// Test df3 on the samples and labels and print the confusion matrix.
cout << "test deserialized function: \n" << test_multiclass_decision_function(df3, samples, labels) << endl;
// Finally, if you want to get the binary classifiers from inside a multiclass decision
// function you can do it by calling get_binary_decision_functions() like so:
one_vs_one_decision_function<ovo_trainer>::binary_function_table functs;
functs = df.get_binary_decision_functions();
cout << "number of binary decision functions in df: " << functs.size() << endl;
// The functs object is a std::map which maps pairs of labels to binary decision
// functions. So we can access the individual decision functions like so:
decision_function<poly_kernel> df_1_2 = any_cast<decision_function<poly_kernel> >(functs[make_unordered_pair(1,2)]);
decision_function<rbf_kernel> df_1_3 = any_cast<decision_function<rbf_kernel> >(functs[make_unordered_pair(1,3)]);
// df_1_2 contains the binary decision function that votes for class 1 vs. 2.
// Similarly, df_1_3 contains the classifier that votes for 1 vs. 3.
// Note that the multiclass decision function doesn't know what kind of binary
// decision functions it contains. So we have to use any_cast to explicitly cast
// them back into the concrete type. If you make a mistake and try to any_cast a
// binary decision function into the wrong type of function any_cast will throw a
// bad_any_cast exception.
}
catch (std::exception& e)
{
cout << "exception thrown!" << endl;
cout << e.what() << endl;
}
}
// ----------------------------------------------------------------------------------------
......
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