def c2min(f, c1, c2):
    """Take the minimum value between two columns in a dataframe.

    Parameters
    ----------
    f : pandas.DataFrame
        Dataframe containing the two columns ``c1`` and ``c2``.
    c1 : str
        Name of the first column in the dataframe ``f``.
    c2 : str
        Name of the second column in the dataframe ``f``.

    Returns
    -------
    min_val : float
        The minimum value of the two columns.

    """
    min_val = min(f[c1], f[c2])
    return min_val
