def abs_p_diff(predict_table, categA='sandwich', categB='sushi'):
    """Calculates the absolute distance between two category predictions

    :param predict_table: as returned by `predict_table`
    :param categA: the first of two categories to compare
    :param categB: the second of two categoreis to compare
    :returns: series with the absolute difference between the predictions
    :rtype: pandas Series

    """
    return abs(predict_table['p_%s' % categA] - predict_table['p_%s' % categB])