如何标记与绘图比例无关的垂直线？

我的程序获取n数据集并绘制它们的直方图。

一、如何标注与地块高度无关的垂直线？

垂直线表示数据集中出现频率最高的值。我想添加一个指示值的标签，比如从顶部开始的 20%。使用时matplotlib.pyplot.text()我必须手动分配x和y值。根据数据集，文本会向上或向下移动，这是我不希望发生的。

matplot.axvline(most_common_number, linewidth=0.5, color='black')
matplot.text(most_common_number + 3, 10, str(most_common_number),
    horizontalalignment='center', fontweight='bold', color='black')

我也尝试设置label参数，matplotlib.pyplot.axvline()但它只会添加到legend情节的。

matplot.axvline(most_common_number, linewidth=0.5, color='black', label=str(most_common_number))

I wonder if there is a way to use percentages so the text appears n% from the top or use a different method to label the vertical lines. Or am I doing this all wrong?

II. How to make the ticks on x-axis to be spaced out better on resulting image?

I want the x-axis ticks to be factors of 16 so I had to override the defaults. This is where the trouble began. When I save the plot to a PNG file, the x-axis looks really messed up.

But when I use show() it works fine:

Program Snippet

kwargs = dict(alpha=0.5, bins=37, range=(0, 304), density=False, stacked=True)
fig, ax1 = matplot.subplots()

colors = ['tab:blue', 'tab:orange', 'tab:green', 'tab:red', 'tab:purple', 'tab:brown', 'tab:pink', 'tab:gray', 'tab:olive', 'tab:cyan']

count = 0
'''
datasets = [('dataset name', ['data'])]
'''
for item in datasets:
    dataset = item[1]
    most_common_number = most_common(dataset)
    ax1.hist(dataset, **kwargs, label=item[0], color=colors[count])
    matplot.axvline(most_common_number, linewidth=0.5, color='black')
    matplot.text(most_common_number + 3, 10, str(most_common_number),
        horizontalalignment='center', fontweight='bold', color='black')
    count += 1

#for x-axis
loc = matplotticker.MultipleLocator(base=16) # this locator puts ticks at regular intervals
ax1.xaxis.set_major_locator(loc)
#for y-axis
y_vals = ax1.get_yticks()
ax1.set_yticklabels(['{:3.1f}%'.format(x / len(datasets[0][1]) * 100) for x in y_vals])

#set title
matplot.gca().set(title='1 vs 2 vs 3')
#set subtitle
matplot.suptitle("This is a cool subtitle.", va="bottom", family="overpass")

matplot.legend()

fig = matplot.gcf()
fig.set_size_inches(16, 9)

matplot.savefig('out.png', format = 'png', dpi=120)
matplot.show()