def effective_leaf_area_index(lai):
    """
    Computes effective leaf area index, this describes the leaf area which
    actively participates in transpiration. It is based on the actual leaf
    area index and an extinction function. So with a higher leaf area index the
    effective leaf area index is a smaller percentage of the total leaf area
    index.

    .. math ::
        I_{lai,eff}=\\frac{I_{lai}}{0.3I_{lai}+1.2}

    Parameters
    ----------
    lai : float
        Leaf area index
        :math:`I_{lai}`
        [-]

    Returns
    -------
    lai_eff : float
        effective leaf area index
        :math:`I_{lai,eff}`
        [-]

    Examples
    --------
    >>> from ETLook import leaf
    >>> leaf.effective_leaf_area_index(3.0)
    1.4285714285714288
    >>> leaf.effective_leaf_area_index(5.0)
    1.8518518518518516

    .. plot:: pyplots/leaf/plot_effective_leaf_area_index.py

    """
    lai_eff = lai / (0.3 * lai + 1.2)
    return lai_eff
