def get_E(data, keys):
    """
    Retrive the E from a dataset
    """
    try:
        Ei = keys.index('Ekine')
    except:
        try:
            Ei = keys.index('E')
        except:
            raise RuntimeError(
                "Error, cannot find key 'Ekine' nor 'E'. Keys are: ", keys)
    E = data[:, (Ei)]
    return E, Ei
