python - 使用日期和 int 值构建散点图的问题

Question

import pandas as pd
import seaborn as sn
import matplotlib.pyplot as plt
from datetime import datetime
import numpy as np

path = r'C:\Users\bossd\OneDrive\Документы\datarn.csv'
df = pd.read_csv(path)
path2 = r'C:\Users\bossd\OneDrive\Документы\pipirka.csv'
df2 = pd.read_csv(path2) 

x = (df2.loc[df2['timestamp'].str.startswith('2015')])
y = df2['cnt']
plt.scatter(x,y)
plt.show()

我想使用包含“2015”作为 x 轴和“cnt”参数的日期构建散点图，这意味着这一天有自行车出租。 但运行代码后我收到此错误

Cell In[47], line 14
     12 x = (df2.loc[df2['timestamp'].str.startswith('2015')])
     13 y = df2['cnt']
---> 14 plt.scatter(x,y)
     15 plt.show()
     17 display(df2)
...
File ~\venv\lib\site-packages\matplotlib\category.py:214, in UnitData.update(self, data)
    212 # check if convertible to number:
    213 convertible = True
--> 214 for val in OrderedDict.fromkeys(data):
    215     # OrderedDict just iterates over unique values in data.
    216     _api.check_isinstance((str, bytes), value=val)
    217     if convertible:
    218         # this will only be called so long as convertible is True.

TypeError: unhashable type: 'numpy.ndarray'

数据帧如下所示，包含时间戳作为日期和 cnt 作为当天自行车租赁的数量

data = {'timestamp': ['2015-01-04', '2015-01-05', '2015-01-06', '2015-01-07', '2015-01-08', '2016-12-27', '2016-12-28', '2016-12-29', '2016-12-30', '2016-12-31'],
        'cnt': [9234, 20372, 20613, 21064, 15601, 10842, 12428, 14052, 11566, 11424]}
df2 = pd.DataFrame(data)

    timestamp    cnt
0  2015-01-04   9234
1  2015-01-05  20372
2  2015-01-06  20613
3  2015-01-07  21064
4  2015-01-08  15601
5  2016-12-27  10842
6  2016-12-28  12428
7  2016-12-29  14052
8  2016-12-30  11566
9  2016-12-31  11424

Answer 1

• 首先应使用 pd.to_datetime 将 'timestamp' 列转换为日期时间数据类型，否则日期时间 x 刻度将无法正确定位和格式化。
  • 典型的流程应从清理数据开始，然后进行选择。
• x = (df2.loc[df2['timestamp'].str.startswith('2015')]) 是错误的原因，因为它选择整个数据帧，而不是数据框的单列。并且未选择所需年份的 df2['cnt']。
• pandas.DataFrame.plot 使用 matplotlib 作为默认绘图后端，应用于绘制数据帧。

# load the sample dataframe from the OP

# convert timestamp to a datetime dtype
df2.timestamp = pd.to_datetime(df2.timestamp)

# select the data by year
df_2015 = df2[df2.timestamp.dt.year.eq(2015)]

# directly plot the dataframe, which uses matplotlib as the back end
ax = df_2015.plot(x='timestamp', marker='.', ls='')

• x 刻度和标签的格式取决于数据范围，可以通过以下答案进行更改
  • Changing the formatting of a datetime axis
  • How to change the datetime tick label frequency
• x 轴限制可以设置如下:
  • How to set xlim and xticks after plotting time-series data