util.py 文件源码

def compute_logarithmic_scale(min_, max_, min_scale, max_scale):
    """Compute an optimal scale for logarithmic"""
    if max_ <= 0 or min_ <= 0:
        return []
    min_order = int(floor(log10(min_)))
    max_order = int(ceil(log10(max_)))
    positions = []
    amplitude = max_order - min_order
    if amplitude <= 1:
        return []
    detail = 10.
    while amplitude * detail < min_scale * 5:
        detail *= 2
    while amplitude * detail > max_scale * 3:
        detail /= 2
    for order in range(min_order, max_order + 1):
        for i in range(int(detail)):
            tick = (10 * i / detail or 1) * 10 ** order
            tick = round_to_scale(tick, tick)
            if min_ <= tick <= max_ and tick not in positions:
                positions.append(tick)
    return positions