def uvc_get_hessian(x, data):
    ' Returns the Hessian of the material model error function for a given set of test data evaluated at x.\n\n    :param np.array x: Updated Voce-Chaboche material model parameters.\n    :param list data: (pd.DataFrame) Stress-strain history for each test considered.\n    :return np.array: Hessian matrix of the error function.\n    '

    def f(xi):
        val = 0.0
        for d in data:
            val += error_single_test_uvc(xi, d)
        return val
    hess_fun = nda.Hessian(f)
    return hess_fun(x)
Returns the Hessian of the material model error function for a given set of test data evaluated at x.

:param np.array x: Updated Voce-Chaboche material model parameters.
:param list data: (pd.DataFrame) Stress-strain history for each test considered.
:return np.array: Hessian matrix of the error function.
def uvc_get_hessian(x, data):
    ' Returns the Hessian of the material model error function for a given set of test data evaluated at x.\n\n    :param np.array x: Updated Voce-Chaboche material model parameters.\n    :param list data: (pd.DataFrame) Stress-strain history for each test considered.\n    :return np.array: Hessian matrix of the error function.\n    '

    def f(xi):
        val = 0.0
        for d in data:
            val += error_single_test_uvc(xi, d)
        return val
    hess_fun = nda.Hessian(f)
    return hess_fun(x)