opencv/modules/ml/test/test_knearest.cpp

// This file is part of OpenCV project.
// It is subject to the license terms in the LICENSE file found in the top-level directory
// of this distribution and at http://opencv.org/license.html.

#include "test_precomp.hpp"

namespace opencv_test { namespace {

using cv::ml::TrainData;
using cv::ml::EM;
using cv::ml::KNearest;

TEST(ML_KNearest, accuracy)
{
    int sizesArr[] = { 500, 700, 800 };
    int pointsCount = sizesArr[0]+ sizesArr[1] + sizesArr[2];

    Mat trainData( pointsCount, 2, CV_32FC1 ), trainLabels;
    vector<int> sizes( sizesArr, sizesArr + sizeof(sizesArr) / sizeof(sizesArr[0]) );
    Mat means;
    vector<Mat> covs;
    defaultDistribs( means, covs );
    generateData( trainData, trainLabels, sizes, means, covs, CV_32FC1, CV_32FC1 );

    Mat testData( pointsCount, 2, CV_32FC1 );
    Mat testLabels;
    generateData( testData, testLabels, sizes, means, covs, CV_32FC1, CV_32FC1 );

    {
        SCOPED_TRACE("Default");
        Mat bestLabels;
        float err = 1000;
        Ptr<KNearest> knn = KNearest::create();
        knn->train(trainData, ml::ROW_SAMPLE, trainLabels);
        knn->findNearest(testData, 4, bestLabels);
        EXPECT_TRUE(calcErr( bestLabels, testLabels, sizes, err, true ));
        EXPECT_LE(err, 0.01f);
    }
    {
        SCOPED_TRACE("KDTree");
        Mat neighborIndexes;
        float err = 1000;
        Ptr<KNearest> knn = KNearest::create();
        knn->setAlgorithmType(KNearest::KDTREE);
        knn->train(trainData, ml::ROW_SAMPLE, trainLabels);
        knn->findNearest(testData, 4, neighborIndexes);
        Mat bestLabels;
        // The output of the KDTree are the neighbor indexes, not actual class labels
        // so we need to do some extra work to get actual predictions
        for(int row_num = 0; row_num < neighborIndexes.rows; ++row_num){
            vector<float> labels;
            for(int index = 0; index < neighborIndexes.row(row_num).cols; ++index) {
                labels.push_back(trainLabels.at<float>(neighborIndexes.row(row_num).at<int>(0, index) , 0));
            }
            // computing the mode of the output class predictions to determine overall prediction
            std::vector<int> histogram(3,0);
            for( int i=0; i<3; ++i )
                ++histogram[ static_cast<int>(labels[i]) ];
            int bestLabel = static_cast<int>(std::max_element( histogram.begin(), histogram.end() ) - histogram.begin());
            bestLabels.push_back(bestLabel);
        }
        bestLabels.convertTo(bestLabels, testLabels.type());
        EXPECT_TRUE(calcErr( bestLabels, testLabels, sizes, err, true ));
        EXPECT_LE(err, 0.01f);
    }
}

TEST(ML_KNearest, regression_12347)
{
    Mat xTrainData = (Mat_<float>(5,2) << 1, 1.1, 1.1, 1, 2, 2, 2.1, 2, 2.1, 2.1);
    Mat yTrainLabels = (Mat_<float>(5,1) << 1, 1, 2, 2, 2);
    Ptr<KNearest> knn = KNearest::create();
    knn->train(xTrainData, ml::ROW_SAMPLE, yTrainLabels);

    Mat xTestData = (Mat_<float>(2,2) << 1.1, 1.1, 2, 2.2);
    Mat zBestLabels, neighbours, dist;
    // check output shapes:
    int K = 16, Kexp = std::min(K, xTrainData.rows);
    knn->findNearest(xTestData, K, zBestLabels, neighbours, dist);
    EXPECT_EQ(xTestData.rows, zBestLabels.rows);
    EXPECT_EQ(neighbours.cols, Kexp);
    EXPECT_EQ(dist.cols, Kexp);
    // see if the result is still correct:
    K = 2;
    knn->findNearest(xTestData, K, zBestLabels, neighbours, dist);
    EXPECT_EQ(1, zBestLabels.at<float>(0,0));
    EXPECT_EQ(2, zBestLabels.at<float>(1,0));
}

TEST(ML_KNearest, bug_11877)
{
    Mat trainData = (Mat_<float>(5,2) << 3, 3, 3, 3, 4, 4, 4, 4, 4, 4);
    Mat trainLabels = (Mat_<float>(5,1) << 0, 0, 1, 1, 1);

    Ptr<KNearest> knnKdt = KNearest::create();
    knnKdt->setAlgorithmType(KNearest::KDTREE);
    knnKdt->setIsClassifier(true);

    knnKdt->train(trainData, ml::ROW_SAMPLE, trainLabels);

    Mat testData = (Mat_<float>(2,2) << 3.1, 3.1, 4, 4.1);
    Mat testLabels = (Mat_<int>(2,1) << 0, 1);
    Mat result;

    knnKdt->findNearest(testData, 1, result);

    EXPECT_EQ(1, int(result.at<int>(0, 0)));
    EXPECT_EQ(2, int(result.at<int>(1, 0)));
    EXPECT_EQ(0, trainLabels.at<int>(result.at<int>(0, 0), 0));
}

}} // namespace