c++ - Convert a std::vector<std::vector <double> > representing a 2D array to cv::Mat -

what elegant , efficient way convert nested std::vector of std::vectors cv::mat? nested structure holding array, i.e. inner std::vectors have same size , represent matrix rows. don't mind data being copied 1 another.

i know single, non-nested std::vector easy, there constructor:

std::vector <double> myvec; cv::mat mymat;  // fill myvec bool copy = true;  mymat = cv::mat(myvec, copy); 

what nested vector?

this way it:

std::vector<double> row1; row1.push_back(1.0); row1.push_back(2.0); row1.push_back(3.0);  std::vector<double> row2; row2.push_back(4.0); row2.push_back(5.0); row2.push_back(6.0);  std::vector<std::vector<double> > vector_of_rows; vector_of_rows.push_back(row1); vector_of_rows.push_back(row2);  // make sure size of of row1 , row2 same, else you'll have serious problems! cv::mat my_mat(vector_of_rows.size(), row1.size(), cv_64f);  (size_t = 0; < vector_of_rows.size(); i++) {        (size_t j = 0; j < row1.size(); j++)     {            my_mat.at<double>(i,j) = vector_of_rows[i][j];     }    }     std::cout << my_mat << std::endl; 

outputs:

[1, 2, 3;   4, 5, 6] 

i tried approach using constructor of mat , push_back() method without success, maybe can figure out. luck!