def sparkline(data):
    '''
    Return a spark line for the given data set.

    :value data: sequence of numeric values

    >>> print sparkline([1, 2, 3, 4, 5, 6, 5, 4, 3, 1, 5, 6])  # doctest: +SKIP
    ▁▂▃▄▅▆▅▄▃▁▅▆

    '''

    min_value = float(min(data))
    max_value = float(max(data))
    steps = (max_value - min_value) / float(len(SPARKCHAR) - 1)
    return ''.join([
        SPARKCHAR[int((float(value) - min_value) / steps)]
        for value in data
    ])