c++ - OpenCV 中的矩阵值是 inf/nan

Question

我正在尝试对一组点使用多项式回归将它们映射到一条曲线。当我构 build 计矩阵时，赋值似乎没有正确进行。构造的矩阵是一个 3 x n 矩阵，其中 n 是点数，与设计矩阵一样，第一列应该全为 1(来自 //HERE IS ASSIGNMENT 部分)。当我打印矩阵时，第一列充满了随机数，而且通常是 infs 和 nans。常量赋值怎么可能？这会导致对矩阵进行任何数学运算时出现更多问题，因为它充满了非数字和信息。

下面的代码是构建矩阵的地方。

for (auto it = lane_lines.begin(); it != lane_lines.end(); it++) {
                        vector<pair<Point, Point> > lines = *it;

                        // Remove random line clusters
                        if (lines.size() < 10) {
                                it = --lane_lines.erase(it);
                                continue;
                        }   

                        Mat design(lines.size() * 2, 3, CV_64FC1);
                        Mat y_vec(lines.size() * 2, 1, CV_64FC1);

                        for (int i = 0; i < lines.size(); i += 2) {
                                // HERE IS ASSIGNMENT
                                design.at<double>(i * 2, 0) = 1.0;
                                design.at<double>(i * 2, 1) = lines[i].first.x;
                                design.at<double>(i * 2, 2) = pow(lines[i].first.x, 2); 
                                design.at<double>(i * 2 + 1, 0) = 1.0;
                                design.at<double>(i * 2 + 1, 1) = lines[i].second.x;
                                design.at<double>(i * 2 + 1, 2) = pow(lines[i].second.x, 2); 

                                y_vec.at<double>(i * 2, 0) = lines[i].first.y;
                                y_vec.at<double>(i * 2 + 1, 0) = lines[i].second.y;
                        }   

                        // TODO: Deal with all the NaNs
                        cout << design << endl;
                        cout << design.t() * design << endl;
                        cout << "DET: " << determinant(design.t() * design) << endl << endl;

                        Mat std_poly = ((design.t() * design).inv() * design.t()) * y_vec;

                        double a = std_poly.at<double>(0, 2); 
                        double b = std_poly.at<double>(0, 1); 
                        double c = std_poly.at<double>(0, 0); 
                        double h = -b / (2 * a == 0 ? numeric_limits<double>::min() : 2 * a); 
                        double k = c - (a * pow(h, 2));

                        tuple<double, double, double, Point> curve(a, b, c, Point(h, k));
                        curves.push_back(curve);
                }

编辑:对于不同的数据集，问题似乎是随机发生的。

Answer 1

首先看一下您的代码:

for (int i = 0; i < lines.size(); i += 2) {
     // HERE IS ASSIGNMENT
     design.at<double>(i * 2, 0) = 1.0;
     design.at<double>(i * 2, 1) = lines[i].first.x;
     design.at<double>(i * 2, 2) = pow(lines[i].first.x, 2); 
     design.at<double>(i * 2 + 1, 0) = 1.0;
     design.at<double>(i * 2 + 1, 1) = lines[i].second.x;
     design.at<double>(i * 2 + 1, 2) = pow(lines[i].second.x, 2); 
     y_vec.at<double>(i * 2, 0) = lines[i].first.y;
     y_vec.at<double>(i * 2 + 1, 0) = lines[i].second.y;
   }   

对于第一次迭代 i=0 这两行

design.at<double>(i * 2, 0) = 1.0;
design.at<double>(i * 2 + 1, 0) = 1.0;

成为:

design.at<double>(0, 0) = 1.0;
design.at<double>(1, 0) = 1.0;

然后下一次迭代是 i=2 因为 i+=2 在循环中所以上面的行变成:

design.at<double>(4, 0) = 1.0;
design.at<double>(5, 0) = 1.0;

我认为您应该将 i+=2 更改为 i++ 以修复该行为。

注意您的代码可能还有其他问题。