我正在尝试将 pandas 数据框中的数据绘制为时间（年）的函数。数据摘要如下所示：           DATE    WALCL0    2010-08-18  23136621    2010-08-25  23010152    2010-09-01  23019963    2010-09-08  23058024    2010-09-15  2296079517  2020-07-15  6958604518  2020-07-22  6964755519  2020-07-29  6949032520  2020-08-05  6945237521  2020-08-12  6957277我尝试使用以下代码绘制数据：import numpy as npimport pandas as pdimport matplotlib.pyplot as pltimport matplotlib.dates as mdatesyears = mdates.YearLocator()   # every yearmonths = mdates.MonthLocator()  # every monthyears_fmt = mdates.DateFormatter('%Y')dfData = pd.read_csv(sPathIn+sFname, skiprows = 0)ax = dfData.plot()ax.xaxis.set_major_locator(years)ax.xaxis.set_major_formatter(years_fmt)ax.xaxis.set_minor_locator(months)datemin = np.datetime64(dfData['DATE'][0], 'Y')datemax = np.datetime64(dfData['DATE'].iloc[-1], 'Y') + np.timedelta64(1, 'Y')ax.set_xlim( datemin, datemax)     plt.show()当我运行此代码时，绘图轴显示正确，但时间序列数据 (WALCL) 未出现。如果我省略ax.set_xlim( datemin, datemax)，则会显示时间序列数据，但 x 轴的格式不再正确（从 1970 年开始一直运行到 1971 年）。这是修改后的代码示例：import numpy as npimport pandas as pdimport matplotlib.pyplot as pltimport matplotlib.dates as mdatesyears = mdates.YearLocator()   # every yearmonths = mdates.MonthLocator()  # every monthyears_fmt = mdates.DateFormatter('%Y')sPathIn = "C:\\Users\\reg\\projects\\notes\\Political_Economy\\S&P+Fed-Assets\\"sFname = "WALCL.csv"这是回溯：Traceback (most recent call last):  File "C:\Users\reg\projects\Notes\Political_Economy\S&P+Fed-Assets\Python\s&p-fed-assets-v0.2.3.py", line 25, in <module>    dfData.set_index('DATE', inplace=True)  File "C:\Users\reg\Anaconda3\lib\site-packages\pandas\core\frame.py", line 4545, in set_index    raise KeyError(f"None of {missing} are in the columns")KeyError: "None of ['DATE'] are in the columns"    # load data    dfData = pd.read_csv(sPathIn+sFname, skiprows = 0, parse_dates=['DATE'], index_col='DATE')        #set up plot fxn    dfData.set_index('DATE', inplace=True)    ax = dfData.plot('DATE', 'WALCL')