缩放时保持绘图内的线标签可见

Question

我正在使用 matplotlibs plt.axvline 在图表上绘制垂直线。我想将垂直线上的标签直接放在图表上，而不是图例中。

我希望我的图表在垂直线上具有如下所示的标签：

如果我放大某个部分，我希望垂直线标签相应地移动，以便它们在屏幕上仍然可见。像这样：

谁能帮我解决这个问题？将不胜感激！

到目前为止我的代码如下：

from astropy.io import fits
from astropy.utils.data import download_file
from astropy.table import Table
import matplotlib.pyplot as plt
import numpy as np

class Spectrum:
    # Let's download the data to plot    
    def __init__(self, url):
        self.url = url
        self.hdu_list = fits.open(download_file(url, cache=True), memmap=False)

    # Now lets plot the data
    def plot_spectra(self):
        x = np.array(Table(self.hdu_list[1].data).columns[1])
        x = 10 ** x
        y = np.array(Table(self.hdu_list[1].data).columns[0])
        plt.plot(x, y, 'k', lw=1)

    # Now lets plot the vertical lines, AND THIS IS WHERE I WANT TO ADD LABELS.
    def plot_spectral_types(self):
        my_type = input("Please enter the spectral type to plot (o, b, a, or f): ")
        if my_type is 'o':
            my_type = o_type
        elif my_type is 'b':
            my_type = b_type
        elif my_type is 'a':
            my_type = a_type
        elif my_type is 'f':
            my_type = f_type

        element, wavelength = zip(*my_type)
# Each vertical line's x value is a wavelength. 
# I want the vertical line's label to be the corresponding element.
        for i in wavelength:
            plt.axvline(linewidth=0.25, color='r', x=i)

o_type = [
('NIII', 4097),
('SiIV', 4089),
('H', 4340.5),
('HeI', 4471),
('HeII', 4541),
('NIII', 4632),
('NIII', 4640),
('CIII', 4650),
('HeII', 4686)
]

b_type = [
('SiIV', 4089),
('H', 4101.7),
('HeI', 4121),
('SiII', 4128),
('SiII', 4131),
('H', 4340.5),
('HeI', 4471),
('CIII', 4540),
('HeII', 4541),
('CIII', 4650),
('H', 4861.33)
]

a_type = [
('CaII (K)', 3933.70),
('CaII', 3968.50),
('H', 3970.10),
('H', 4101.70),
('HeI', 4121.00),
('SiII', 4128.00),
('SiII', 4131.00),
('FeI', 4299.00),
('FeI', 4303.00),
('TiII', 4303.00),
('H', 4340.50),
('MgII', 4481.00),
('H', 4861.30),
('H', 6562.70)
]

f_type = [
('CaII', 3933.70),
('CaII', 3968.50),
('H', 3970.10),
('H', 4101.70),
('HeI', 4121.00),
('SiII', 4128.00),
('SiII', 4131.00),
('CaI', 4227.00),
('FeI', 4299.00),
('FeI', 4303.00),
('H', 4340.50),
('CH', 4314.00),
('MgII', 4481.00),
('H', 4861.30),
('H', 6562.70)
]

Answer 1

文本标签默认位于 data-coordinates 中，这可能是您遇到的问题。您可以将 y 值转换为图形坐标，该坐标在缩放时相对于当前轴，并将 x 坐标保留在数据坐标中。一个更独立的（参见 MCVE）示例：

from numpy.random import uniform
from math import sin, pi
import matplotlib.pyplot as plt
import matplotlib.transforms as transforms



fig, ax = plt.subplots()

transDA = transforms.blended_transform_factory(
    ax.transData, ax.transAxes) #  from the transforms tutorial

spectrum = uniform(0,1, 1000) + map(lambda x: sin(2*pi*x/800), range(1000)) #dummy data

ax.plot(range(4000,5000,1), spectrum )

o_type = [
('NIII', 4097),
('SiIV', 4089),
('H', 4340.5),
('HeI', 4471),
('HeII', 4541),
('NIII', 4632),
('NIII', 4640),
('CIII', 4650),
('HeII', 4686)
]

for wavelength in o_type:
        print(wavelength[0],wavelength[1])
        plt.axvline(linewidth=0.25, color='r', x=wavelength[1])
        plt.text(wavelength[1], # x-value from data
                 uniform(0,1), # wiggle the labels 2so they don't overlap
                 wavelength[0], # string label
                 transform = transDA,
                 color='red',
                 family='serif') # the III looked better serif.

原剧情。请注意，前两个标签分别位于图片的一半左右和图片的四分之一处：
放大后，这些标签已随缩放的 x 轴正确移动，但仍位于图的一半和四分之一处：

缩放时保持绘图内的线标签可见

Keep line labels within plot visible when zooming

python

matplotlib

labels