OpenCV expm() function-CodePudding

OpenCV has a exp(inMat, outMat) function that returns a matrix where each cell, (i,j) is exp(inMat.at<>(i, j)).

Is there a function that returns actually the exponent of a matrix (i.e., e^A)?

In MATLAB the function is expm(A).

CodePudding user response：

There is no function, however, it is possible to decompose the matrix into eigenvalues and use the exp(inMat, outMat) function, namely,

void expm(const Mat& m0, Mat& m1)
{
    Mat eval, evec;
    cv::eigenNonSymmetric(m0, eval, evec);

    Mat eveci = evec.t().inv();
    Mat exp_eval;
    cv::exp(eval, exp_eval);
    m1 = evec.t() * Mat::diag(exp_eval) * eveci;
}

Usage example:

    double a[] = {0, 1, -3, 4};
    Mat m0(2, 2, CV_64FC1, a);
    Mat m1(2, 2, CV_64FC1);
    cout << "Matrix m0 : \n" << m0 << "\n";
    expm(m0, m1);
    cout << "Matrix m1 : \n" << m1 << "\n";