matplotlib获取ylim值

问题:matplotlib获取ylim值

matplotlib用来从Python 绘制数据(使用ploterrorbar函数)。我必须绘制一组完全独立的图,然后调整它们的ylim值,以便可以轻松地对其进行视觉比较。

如何ylim从每个图检索值,以便分别取下和上ylim值的最小值和最大值,并调整图以便可以对其进行直观比较?

当然,我可以分析数据并提出自己的自定义ylim值…但是我想用它matplotlib来为我做这些。关于如何轻松(高效)执行此操作的任何建议?

这是我的Python函数,使用绘制matplotlib

import matplotlib.pyplot as plt

def myplotfunction(title, values, errors, plot_file_name):

    # plot errorbars
    indices = range(0, len(values))
    fig = plt.figure()
    plt.errorbar(tuple(indices), tuple(values), tuple(errors), marker='.')

    # axes
    axes = plt.gca()
    axes.set_xlim([-0.5, len(values) - 0.5])
    axes.set_xlabel('My x-axis title')
    axes.set_ylabel('My y-axis title')

    # title
    plt.title(title)

    # save as file
    plt.savefig(plot_file_name)

    # close figure
    plt.close(fig)

I’m using matplotlib to plot data (using plot and errorbar functions) from Python. I have to plot a set of totally separate and independent plots, and then adjust their ylim values so they can be easily visually compared.

How can I retrieve the ylim values from each plot, so that I can take the min and max of the lower and upper ylim values, respectively, and adjust the plots so they can be visually compared?

Of course, I could just analyze the data and come up with my own custom ylim values… but I’d like to use matplotlib to do that for me. Any suggestions on how to easily (and efficiently) do this?

Here’s my Python function that plots using matplotlib:

import matplotlib.pyplot as plt

def myplotfunction(title, values, errors, plot_file_name):

    # plot errorbars
    indices = range(0, len(values))
    fig = plt.figure()
    plt.errorbar(tuple(indices), tuple(values), tuple(errors), marker='.')

    # axes
    axes = plt.gca()
    axes.set_xlim([-0.5, len(values) - 0.5])
    axes.set_xlabel('My x-axis title')
    axes.set_ylabel('My y-axis title')

    # title
    plt.title(title)

    # save as file
    plt.savefig(plot_file_name)

    # close figure
    plt.close(fig)

回答 0

只是使用axes.get_ylim(),它非常类似于set_ylim。从文档

get_ylim()

获取y轴范围[底部,顶部]

Just use axes.get_ylim(), it is very similar to set_ylim. From the docs:

get_ylim()

Get the y-axis range [bottom, top]


回答 1

 ymin, ymax = axes.get_ylim()

如果plt直接使用api,则可以避免完全调用轴:

def myplotfunction(title, values, errors, plot_file_name):

    # plot errorbars
    indices = range(0, len(values))
    fig = plt.figure()
    plt.errorbar(tuple(indices), tuple(values), tuple(errors), marker='.')

    plt.xlim([-0.5, len(values) - 0.5])
    plt.xlabel('My x-axis title')
    plt.ylabel('My y-axis title')

    # title
    plt.title(title)

    # save as file
    plt.savefig(plot_file_name)

   # close figure
    plt.close(fig)
 ymin, ymax = axes.get_ylim()

If you are using the plt api directly, you can avoid calls to the axes altogether:

def myplotfunction(title, values, errors, plot_file_name):

    # plot errorbars
    indices = range(0, len(values))
    fig = plt.figure()
    plt.errorbar(tuple(indices), tuple(values), tuple(errors), marker='.')

    plt.xlim([-0.5, len(values) - 0.5])
    plt.xlabel('My x-axis title')
    plt.ylabel('My y-axis title')

    # title
    plt.title(title)

    # save as file
    plt.savefig(plot_file_name)

   # close figure
    plt.close(fig)

回答 2

利用上面的好答案,并假设您仅按如下方式使用plt

import matplotlib.pyplot as plt

那么您可以使用plt.axis()以下示例中的方法获得所有四个绘图限制。

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5, 6, 7, 8]  # fake data
y = [1, 2, 3, 4, 3, 2, 5, 6]

plt.plot(x, y, 'k')

xmin, xmax, ymin, ymax = plt.axis()

s = 'xmin = ' + str(round(xmin, 2)) + ', ' + \
    'xmax = ' + str(xmax) + '\n' + \
    'ymin = ' + str(ymin) + ', ' + \
    'ymax = ' + str(ymax) + ' '

plt.annotate(s, (1, 5))

plt.show()

上面的代码应产生以下输出图。

Leveraging from the good answers above and assuming you were only using plt as in

import matplotlib.pyplot as plt

then you can get all four plot limits using plt.axis() as in the following example.

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5, 6, 7, 8]  # fake data
y = [1, 2, 3, 4, 3, 2, 5, 6]

plt.plot(x, y, 'k')

xmin, xmax, ymin, ymax = plt.axis()

s = 'xmin = ' + str(round(xmin, 2)) + ', ' + \
    'xmax = ' + str(xmax) + '\n' + \
    'ymin = ' + str(ymin) + ', ' + \
    'ymax = ' + str(ymax) + ' '

plt.annotate(s, (1, 5))

plt.show()

The above code should produce the following output plot.