转换错误：无法将值转换为轴单位：“2015-01-01”

Question

我正在尝试将值转换为轴单位。我检查了具有类似问题的代码，但没有一个解决了这个特定的挑战。如下图所示，预期图 (A) 应该在 x 轴上显示月份（一月、二月等），但图 (B) 中却显示日期（2015 年 1 月等）。

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下面是源码，请帮忙。谢谢。

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plt.rcParams["font.size"] = 18\n\nplt.figure(figsize=(20,5))\nplt.plot(df.air_temperature,label="Air temperature at Frankfurt Int. Airport in 2015")\nplt.xlim(("2015-01-01","2015-12-31"))\nplt.xticks(["2015-{:02d}-15".format(x) for x in range(1,13,1)],["Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"])\nplt.legend()\nplt.ylabel("Temperature (\xc2\xb0C)")\nplt.show()\n\n

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Answer 1

使用日期时间绘制绘图的明智方法是使用datetimeformat 代替str; 因此，首先，您应该进行此转换：

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df = pd.read_csv(r\'data/frankfurt_weather.csv\')\ndf[\'time\'] = pd.to_datetime(df[\'time\'], format = \'%Y-%m-%d %H:%M\')\n

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然后您可以根据需要设置绘图，最好遵循面向对象的界面：

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plt.rcParams[\'font.size\'] = 18\nfig, ax = plt.subplots(figsize = (20,5))\n\nax.plot(df[\'time\'], df[\'air_temperature\'], label = \'Air temperature at Frankfurt Int. Airport in 2015\')\n\nax.legend()\nax.set_ylabel(\'Temperature (\xc2\xb0C)\')\n\nplt.show()\n

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然后您可以自定义：

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• x 勾选标签格式和位置matplotlib.dates：

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  ax.xaxis.set_major_locator(md.MonthLocator(interval = 1))\nax.xaxis.set_major_formatter(md.DateFormatter(\'%b\'))\n

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• x 轴限制：

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  ax.set_xlim([pd.to_datetime(\'2015-01-01\', format = \'%Y-%m-%d\'),\n             pd.to_datetime(\'2015-12-31\', format = \'%Y-%m-%d\')])\n

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• x 的大写第一个字母勾选月份标签名称

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  fig.canvas.draw()\nax.set_xticklabels([month.get_text().title() for month in ax.get_xticklabels()])\n

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完整代码

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import pandas as pd\nimport matplotlib.pyplot as plt\nimport matplotlib.dates as md\n\n\ndf = pd.read_csv(r\'data/frankfurt_weather.csv\')\ndf[\'time\'] = pd.to_datetime(df[\'time\'], format = \'%Y-%m-%d %H:%M\')\n\n\nplt.rcParams[\'font.size\'] = 18\nfig, ax = plt.subplots(figsize = (20,5))\n\nax.plot(df[\'time\'], df[\'air_temperature\'], label = \'Air temperature at Frankfurt Int. Airport in 2015\')\n\nax.legend()\nax.set_ylabel(\'Temperature (\xc2\xb0C)\')\n\nax.xaxis.set_major_locator(md.MonthLocator(interval = 1))\nax.xaxis.set_major_formatter(md.DateFormatter(\'%b\'))\n\nax.set_xlim([pd.to_datetime(\'2015-01-01\', format = \'%Y-%m-%d\'),\n             pd.to_datetime(\'2015-12-31\', format = \'%Y-%m-%d\')])\n\nfig.canvas.draw()\nax.set_xticklabels([month.get_text().title() for month in ax.get_xticklabels()])\n\nplt.show()\n

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