Question

我最近将matplotlib从3.1.2升级到了3.3.0，并遇到了此错误（我在3.1.2上没有得到）：“ ValueError：s必须是标量，或与x和y”。在下面的示例中，我只是试图分散绘制pandas groupby对象，并且所有列都具有相同数量的值和相同尺寸。

import pandas as pd
import numpy as np
import sys, os, time
import matplotlib.pyplot as plt

headers=['Cpl Time','ECT','PendAtStart','OpCode']
tableData=[[1,111.1,11,'Read'],[2,222.2,22,'Write'],[3,333.3,33,'Read'],[4,444.4,44,'Write'],[5,555.5,55,'Read']]
df = pd.DataFrame(tableData,columns=headers)

cols = ['ECT','PendAtStart','Cpl Time']
print("{:20} Shape, Len".format('Column'))
for col in df.columns:
    print("{:20} {},  {}".format(col, df[col].shape, len(df[col])))

plt.rcParams['figure.figsize'] = [15,10]
fig, ax = plt.subplots()

currMarker=0
grouped = df.groupby('OpCode')
for key, group in grouped:
        group.plot(ax=ax, kind='scatter', x='Cpl Time', y='ECT', label=key, s=grouped.PendAtStart) 
plt.show()

即使我更改该行以尝试对x，y和s使用SAME精确列：

group.plot(ax=ax, kind='scatter', x='ECT', y='ECT', label=key, s=grouped['ECT'])

它仍然返回错误（回溯）：

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-54-195485ba7482> in <module>
      6 for key, group in grouped:
      7         print("Key:{}".format(key))
----> 8         group.plot(ax=ax, kind='scatter', x='Cpl Time', y='ECT', label=key, s=df.PendAtStart)
      9 plt.show()

c:\users\klo75358\appdata\local\programs\python\python37\lib\site-packages\pandas\plotting\_core.py in __call__(self, *args, **kwargs)
    736         if kind in self._dataframe_kinds:
    737             if isinstance(data, ABCDataFrame):
--> 738                 return plot_backend.plot(data, x=x, y=y, kind=kind, **kwargs)
    739             else:
    740                 raise ValueError(

c:\users\klo75358\appdata\local\programs\python\python37\lib\site-packages\pandas\plotting\_matplotlib\__init__.py in plot(data, kind, **kwargs)
     60             kwargs["ax"] = getattr(ax, "left_ax", ax)
     61     plot_obj = PLOT_CLASSES[kind](data, **kwargs)
---> 62     plot_obj.generate()
     63     plot_obj.draw()
     64     return plot_obj.result

c:\users\klo75358\appdata\local\programs\python\python37\lib\site-packages\pandas\plotting\_matplotlib\core.py in generate(self)
    279         self._compute_plot_data()
    280         self._setup_subplots()
--> 281         self._make_plot()
    282         self._add_table()
    283         self._make_legend()

c:\users\klo75358\appdata\local\programs\python\python37\lib\site-packages\pandas\plotting\_matplotlib\core.py in _make_plot(self)
    967             label=label,
    968             cmap=cmap,
--> 969             **self.kwds
    970         )
    971         if cb:

c:\users\klo75358\appdata\local\programs\python\python37\lib\site-packages\matplotlib\__init__.py in inner(ax, data, *args, **kwargs)
   1429     def inner(ax, *args, data=None, **kwargs):
   1430         if data is None:
-> 1431             return func(ax, *map(sanitize_sequence, args), **kwargs)
   1432
   1433         bound = new_sig.bind(ax, *args, **kwargs)

c:\users\klo75358\appdata\local\programs\python\python37\lib\site-packages\matplotlib\cbook\deprecation.py in wrapper(*inner_args, **inner_kwargs)
    409                          else deprecation_addendum,
    410                 **kwargs)
--> 411         return func(*inner_args, **inner_kwargs)
    412
    413     return wrapper

c:\users\klo75358\appdata\local\programs\python\python37\lib\site-packages\matplotlib\axes\_axes.py in scatter(self, x, y, s, c, marker, cmap, norm, vmin, vmax, alpha, linewidths, verts, edgecolors, plotnonfinite, **kwargs)
   4446         s = np.ma.ravel(s)
   4447         if len(s) not in (1, x.size):
-> 4448             raise ValueError("s must be a scalar, or the same size as x and y")
   4449
   4450         c, colors, edgecolors = \

ValueError: s must be a scalar, or the same size as x and y

同样，在Matplotlib 3.1.2中，此代码段生成了一个图形并且没有错误...任何建议/输入将不胜感激！

Answer 1

s的大小必须与x和y相同。您不能使用s=df.PendAtStart，因为df是原始数据帧，并且只需要一组。因此，您需要s=group.PendAtStart。

请注意，由于熊猫散布图的限制，您不能仅给出列名。参见this github issue。

Matplotlib升级后出现错误：“ ValueError：s必须为标量，或与x和y相同的大小”

1 个答案: