如何从文件中绘制多条垂直线？

Question

我一直在尝试使用matplotlib为我的绘图添加垂直线，然后在它们之间添加填充。

• thresh_f是文件的名称
• thresh_f只有两列

当文件有多行

时，下面的代码会出错

start, end = np.loadtxt(thresh_f, usecols = [0,1], unpack = True)
ax.axvspan(start, end, alpha=0.3, color='y')

我收到错误：

  

'bool'对象没有属性'any'

我无法理解这意味着什么。

Answer 1

The problem is that your variables start and end become arrays when file has more then one lines. You have to improve your code like:

start, end = np.loadtxt(thresh_f, usecols = [0,1], unpack = True)
ax = plt.gca()
print (start, end) # test data [ 0.  5.] [ 1.  6.]
# check the type of start variable
# loadtxt may return np.ndarray variable
if type(start) is list or type(start) is tuple or type(start) is np.ndarray:
    for s, e in zip(start, end):
        ax.axvspan(s, e, alpha=0.3, color='y')   # many rows, iterate over start and end
else:
    ax.axvspan(start, end, alpha=0.3, color='y') # single line

plt.show()

Answer 2

If you want to avoid the if-else statement, you can pass ndmin = 2 to np.loadtext(). This assures that your start and end are always iterable.

import numpy as np
from matplotlib import pyplot as plt

fig, ax = plt. subplots(1,1)

thresh_f = 'thresh_f.txt'
starts, ends = np.loadtxt(thresh_f, usecols = [0,1], unpack = True, ndmin = 2)

for start, end in zip(starts, ends):
    ax.axvspan(start, end, alpha=0.3, color='y')

plt.show()

Here the results for one and two lines of text: