//Train model with a regression dataset
void CARTTrainer::train(ModelType& model, RegressionDataset const& dataset)
{
//Store the number of input dimensions
m_inputDimension = inputDimension(dataset);
//Pass input dimension (i.e., number of attributes) to tree model
model.setInputDimension(m_inputDimension);
//Store the size of the labels
m_labelDimension = labelDimension(dataset);
// create cross-validation folds
RegressionDataset set=dataset;
CVFolds<RegressionDataset > folds = createCVSameSize(set, m_numberOfFolds);
double bestErrorRate = std::numeric_limits<double>::max();
CARTClassifier<RealVector>::TreeType bestTree;
for (unsigned fold = 0; fold < m_numberOfFolds; ++fold){
//Run through all the cross validation sets
RegressionDataset dataTrain = folds.training(fold);
RegressionDataset dataTest = folds.validation(fold);
std::size_t numTrainElements = dataTrain.numberOfElements();
AttributeTables tables = createAttributeTables(dataTrain.inputs());
std::vector < RealVector > labels(numTrainElements);
boost::copy(dataTrain.labels().elements(),labels.begin());
//Build tree form this fold
CARTClassifier<RealVector>::TreeType tree = buildTree(tables, dataTrain, labels, 0, dataTrain.numberOfElements());
//Add the tree to the model and prune
model.setTree(tree);
while(true){
//evaluate the error of current tree
SquaredLoss<> loss;
double error = loss.eval(dataTest.labels(), model(dataTest.inputs()));
if(error < bestErrorRate){
//We have found a subtree that has a smaller error rate when tested!
bestErrorRate = error;
bestTree = tree;
}
if(tree.size() == 1) break;
pruneTree(tree);
model.setTree(tree);
}
}
SHARK_CHECK(bestTree.size() > 0, "We should never set a tree that is empty.");
model.setTree(bestTree);
}
int main(int argc, char **argv) {
RegressionDataset data;
importCSV(data, "blogData_train.csv", LAST_COLUMN,1,',','#', 2<<16);
LinearRegression trainer(100);
LinearModel<> model;
Timer time;
trainer.train(model, data);
double time_taken = time.stop();
SquaredLoss<> loss;
cout << "Residual sum of squares:" << loss(data.labels(),model(data.inputs()))<<std::endl;
cout << "Time:\n" << time_taken << endl;
cout << time_taken << endl;
}