matplotlib text（）未显示在打印中

Question

我无法在绘图中显示文字，axhline（）显示文字，但无法显示文字（）。我对熊猫和matplotlib还不熟悉，显然我不了解一些东西

# df is a pandas Dataframe

df_last_24 = df[df['Date']>=(dt.datetime.now()-dt.timedelta(hours=24))]

ax = df_last_24.plot.line(x="Date",title="Air Qualty Index over the last 24 hours")

# Define the date format
years_fmt = mdates.DateFormatter('%I:%M %p')
ax.xaxis.set_major_formatter(years_fmt)


plot.axhline(linewidth=4,y=300, color='#731425', linestyle='-')
plot.text(0, 300, 'Hazardous', fontsize=10, va='center', ha='left', backgroundcolor='w')

plot.axhline(linewidth=4,y=200, color='#8c1a4b', linestyle='-')
plot.text(0, 200, 'Very Unhealthy', fontsize=10, va='center', ha='left', backgroundcolor='w')

plot.axhline(linewidth=4,y=150, color='#951d47', linestyle='-')
plot.text(0, 150, 'Unhealthy', fontsize=10, va='center', ha='left', backgroundcolor='w')

plot.axhline(linewidth=4,y=100, color='#e23127', linestyle='-')
plot.text(0, 100, 'Unhealthy to Sensitive Groups', fontsize=10, va='center', ha='left', backgroundcolor='w')

plot.axhline(linewidth=4,y=50, color='#f29d3a', linestyle='-')
plot.text(0, 50, 'Moderate', fontsize=10, va='center', ha='left', backgroundcolor='w')

plot.show(block=True)

Answer 1

plt.axhline()和plt.是正确的描述。其他图表可能因缺少提供的数据而受到影响。请检查一下这个

import matplotlib.pyplot as plt

plt.axhline(linewidth=4,y=300, color='#731425', linestyle='-')
plt.text(0, 300, 'Hazardous', fontsize=10, va='center', ha='left', backgroundcolor='w')

plt.axhline(linewidth=4,y=200, color='#8c1a4b', linestyle='-')
plt.text(0, 200, 'Very Unhealthy', fontsize=10, va='center', ha='left', backgroundcolor='w')

plt.axhline(linewidth=4,y=150, color='#951d47', linestyle='-')
plt.text(0, 150, 'Unhealthy', fontsize=10, va='center', ha='left', backgroundcolor='w')

plt.axhline(linewidth=4,y=100, color='#e23127', linestyle='-')
plt.text(0, 100, 'Unhealthy to Sensitive Groups', fontsize=10, va='center', ha='left', backgroundcolor='w')

plt.axhline(linewidth=4,y=50, color='#f29d3a', linestyle='-')
plt.text(0, 50, 'Moderate', fontsize=10, va='center', ha='left', backgroundcolor='w')

plt.show(block=True)

Answer 2

问题是数据帧图中的x坐标是时间。使用min（）和datestr2num（）似乎可以解决这个问题

# Find Date/Time Range
column = df_last_24['Date/Time'].dt.strftime('%a %b %d %H:%M')
subtitle = column.min() + " - " +column.max()
text_x = mdates.datestr2num(column.min())

...

# Add Level lines and Labels
ax.axhline(linewidth=4,y=300, color='#731425', linestyle='-')
ax.text(text_x, 300, 'Hazardous', fontsize=10, va='center', ha='left', backgroundcolor='w')