numpy - Python matplotlib 画直方图出错？

问题描述

sql3 = ’select sum(comment_num) as total_col,create_time from article GROUP BY create_time’df = pd.read_sql(sql3, conn)print(df)# 总数# N = 22# 宽度width = 0.45# ind = np.arange(N)plt.bar(df[’create_time’], df[’total_col’], width, color=’r’, label=’total_col’)plt.xlabel(u'发表日期')plt.ylabel(u'总评论数')plt.title(u'每日发表文章的总评论数直方分布图')plt.legend()plt.show()

df：

total_col create_time0 2.0 2017-04-271 0.0 2017-05-092 3.0 2017-05-103 6.0 2017-05-114 3.0 2017-05-125 2.0 2017-05-136 1.0 2017-05-147 0.0 2017-05-158 5.0 2017-05-169 0.0 2017-05-17101.0 2017-05-18110.0 2017-05-19126.0 2017-05-22130.0 2017-05-24141.0 2017-05-25150.0 2017-05-26166.0 2017-05-27174.0 2017-05-2918 16.0 2017-05-31194.0 2017-06-02202.0 2017-06-04211.0 2017-06-05

错误：

Traceback (most recent call last): File 'D:/PyCharm/py_scrapyjobbole/data_analysis.py', line 46, in <module> plt.bar(df[’create_time’], df[’total_col’], width, color=’r’, label=’total_col’) File 'D:python-3.5.2libsite-packagesmatplotlibpyplot.py', line 2704, in bar **kwargs) File 'D:python-3.5.2libsite-packagesmatplotlib__init__.py', line 1898, in inner return func(ax, *args, **kwargs) File 'D:python-3.5.2libsite-packagesmatplotlibaxes_axes.py', line 2105, in bar left = [left[i] - width[i] / 2. for i in xrange(len(left))] File 'D:python-3.5.2libsite-packagesmatplotlibaxes_axes.py', line 2105, in <listcomp> left = [left[i] - width[i] / 2. for i in xrange(len(left))]TypeError: unsupported operand type(s) for -: ’datetime.date’ and ’float’

问题解答

試試astype()轉換型別，參見stackoverflow

%matplotlib inlineimport pandas as pddf = pd.DataFrame.from_csv(’timeseries.tsv’, sep='t')df[’total_col’] = df[’total_col’].astype(float)df[’create_time’] = df[’create_time’].astype(’datetime64[D]’)df.set_index([’create_time’]).plot(kind=’bar’)

plt.bar(df[’create_time’], df[’total_col’], width, color=’r’, label=’total_col’)

里面的left, height参数应该是数值形的list，你现在df[’create_time’]传递的是时间类型的列表