Python绘图y轴平均标签不会显示并且日期都很拥挤

Question

我想要为红色 y 轴平均线添加一个标签，但它不会显示为标签。此外，数据集中的所有日期都是众包

这是我的代码:

def plot_data(measurement):


    df = pd.read_csv("out.csv")
    date = df["date"]
    value = df[measurement]

    plt.plot(date, value, label=host[0:7] + ", " + measurement + ", " + date_til[0:10] + " " +  date_from[11:19] + "-" + date_til[11:19])
    plt.title(measurement)
    plt.xlabel("date")
    plt.ylabel(measurement)
    plt.legend()
    plt.xticks(rotation=45)

    average = df[measurement].mean()

    plt.axhline(y=average, color='r', linestyle='-', label="average Ø ≈ " + str(average))

    fig = plt.gcf()
    fig.set_size_inches(18.5, 10.5, forward=True)

    #today = date.today()
    #print(today)
    filename = "plots/plot_" + date_from[0:10] + ".png"

    fig.savefig(filename, dpi=100)

    print("\rPlot: Done ✔️")

这是情节的结果:

Answer 1

为了在图例中显示average Ø ≈ ...标签，您需要在ax.axhline之后调用plt.legend:

...

average = df[measurement].mean()

plt.axhline(y=average, color='r', linestyle='-', label="average Ø ≈ " + str(average))

plt.legend()

...

---

当您将 x 轴绘制为 str 代替 datetime 时，会发生 x 轴标签拥挤，因此您需要使用 pandas.to_datetime 进行此转换。首先:

df = pd.read_csv(r'data/data.csv')

fig, ax = plt.subplots()

ax.plot(df['date'], df['value'])

plt.show()

df = pd.read_csv(r'data/data.csv')
df['date'] = pd.to_datetime(df['date'])

fig, ax = plt.subplots()

ax.plot(df['date'], df['value'])

plt.show()

---

您可以通过以下方式进一步自定义 x 轴刻度:

import matplotlib.dates as md

# set spacing between ticks
ax.xaxis.set_major_locator(md.HourLocator(interval = 3))

# set tick label format
ax.xaxis.set_major_formatter(md.DateFormatter('%H:%M:%S'))

# set tick label rotation to 45°
plt.setp(ax.xaxis.get_majorticklabels(), rotation = 45)