def rate(totflux, pi, qminus):
    r"""Transition rate for reaction A to B.

    Parameters
    ----------
    totflux : float
        The total flux between reactant and product
    pi : (M,) ndarray
        Stationary distribution
    qminus : (M,) ndarray
        Backward comittor

    Returns
    -------
    kAB : float
        The reaction rate (per time step of the
        Markov chain)

    See also
    --------
    committor, total_flux, flux_matrix

    Notes
    -----
    Computation of the rate relies on discrete transition path theory
    (TPT). The transition rate, i.e. the total number of reaction events per
    time step, is given in [1] as:

    .. math:: k_{AB}=\frac{1}{F} \sum_i \pi_i q_i^{(-)}

    :math:`F` is the total flux for the transition from :math:`A` to
    :math:`B`.

    References
    ----------
    .. [1] F. Noe, Ch. Schuette, E. Vanden-Eijnden, L. Reich and
        T. Weikl: Constructing the Full Ensemble of Folding Pathways
        from Short Off-Equilibrium Simulations.
        Proc. Natl. Acad. Sci. USA, 106, 19011-19016 (2009)

    """
    return dense.tpt.rate(totflux, pi, qminus)