seaborn.violinplot() KeyError 的未知原因

Question

我正在为 Kaggle 上的房价竞赛创建探索性数据分析，但遇到了 seaborn.violinplot() 函数的问题：

我想用函数绘制LotFrontage，但出现以下错误：

sns.violinplot(data=houseprices_num['LotFrontage'], inner='quartile', color='white')

KeyError                                  Traceback (most recent call last)
~\anaconda3\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
   2894             try:
-> 2895                 return self._engine.get_loc(casted_key)
   2896             except KeyError as err:

pandas\_libs\index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas\_libs\index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas\_libs\hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()

pandas\_libs\hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()

KeyError: 0

The above exception was the direct cause of the following exception:

KeyError                                  Traceback (most recent call last)
<ipython-input-31-01b815903af9> in <module>
      1 #houseprices_lfnotna = houseprices[houseprices['LotFrontage'].notna()]
----> 2 sns.violinplot(data=houseprices_num['LotFrontage'], inner='quartile', color='white')

~\anaconda3\lib\site-packages\seaborn\_decorators.py in inner_f(*args, **kwargs)
     44             )
     45         kwargs.update({k: arg for k, arg in zip(sig.parameters, args)})
---> 46         return f(**kwargs)
     47     return inner_f
     48 

~\anaconda3\lib\site-packages\seaborn\categorical.py in violinplot(x, y, hue, data, order, hue_order, bw, cut, scale, scale_hue, gridsize, width, inner, split, dodge, orient, linewidth, color, palette, saturation, ax, **kwargs)
   2385 ):
   2386 
-> 2387     plotter = _ViolinPlotter(x, y, hue, data, order, hue_order,
   2388                              bw, cut, scale, scale_hue, gridsize,
   2389                              width, inner, split, dodge, orient, linewidth,

~\anaconda3\lib\site-packages\seaborn\categorical.py in __init__(self, x, y, hue, data, order, hue_order, bw, cut, scale, scale_hue, gridsize, width, inner, split, dodge, orient, linewidth, color, palette, saturation)
    520                  color, palette, saturation):
    521 
--> 522         self.establish_variables(x, y, hue, data, orient, order, hue_order)
    523         self.establish_colors(color, palette, saturation)
    524         self.estimate_densities(bw, cut, scale, scale_hue, gridsize)

~\anaconda3\lib\site-packages\seaborn\categorical.py in establish_variables(self, x, y, hue, data, orient, order, hue_order, units)
     96                 if hasattr(data, "shape"):
     97                     if len(data.shape) == 1:
---> 98                         if np.isscalar(data[0]):
     99                             plot_data = [data]
    100                         else:

~\anaconda3\lib\site-packages\pandas\core\series.py in __getitem__(self, key)
    880 
    881         elif key_is_scalar:
--> 882             return self._get_value(key)
    883 
    884         if is_hashable(key):

~\anaconda3\lib\site-packages\pandas\core\series.py in _get_value(self, label, takeable)
    987 
    988         # Similar to Index.get_value, but we do not fall back to positional
--> 989         loc = self.index.get_loc(label)
    990         return self.index._get_values_for_loc(self, loc, label)
    991 

~\anaconda3\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
   2895                 return self._engine.get_loc(casted_key)
   2896             except KeyError as err:
-> 2897                 raise KeyError(key) from err
   2898 
   2899         if tolerance is not None:

KeyError: 0

之前对 houseprices_num 所做的修改可能（但不可能）导致错误：

traindf = pd.read_csv('.\\train.csv', sep=',', header=1, index_col='Id')
testdf = pd.read_csv('.\\test.csv', sep=',', header=0, index_col='Id')
houseprices = pd.concat([traindf, testdf], axis=0)
houseprices_num = houseprices[['LotFrontage', 'LotArea', 'MasVnrArea', 'BsmtFinSF1', 'BsmtFinSF2', 'BsmtUnfSF',
                              'TotalBsmtSF', '1stFlrSF', '2ndFlrSF', 'LowQualFinSF', 'GrLivArea', 'GarageArea', 'WoodDeckSF', 'OpenPorchSF', 'EnclosedPorch',
                              '3SsnPorch', 'ScreenPorch', 'PoolArea', 'MiscVal', 'SalePrice']]

从错误消息中，我怀疑 inner= kwarg 可能是负责任的，但根据 seaborn 文档，'quartile' 是一个有效参数。我还尝试在没有空值的情况下绘制LotFrontage，但没有成功。

我希望能解释一下这个错误，以及如何解决它。 谢谢！

Answer 1

如果你真的只想要1把小提琴来看看这个专栏的分布，你可以这样做：

import seaborn as sns
import numpy as np
sns.violinplot(data=houseprices_num['LotFrontage'].values, 
inner='quartile', color='white')

我认为如果您调用数据框会导致一些问题。如果您想将小提琴情节转为其他类别，您可以这样做：

houseprices_num['GarageArea_bin'] = pd.cut(houseprices_num['GarageArea'],2,
labels=['A','B'])
sns.violinplot(data=houseprices_num,x='GarageArea_bin',y='LotFrontage',
inner='quartile', color='white')

Answer 2

小提琴图接收数字数据。您提供要绘制的 x 和 y 变量。

 sns.violinplot(data=houseprices_num,y="LoadFrontageDRG Definition", x="LotArea")
 plt.show()

 #or for one violin plot

 sns.violinplot(houseprices_num["LoadFrontageDRG Definition"])

 plt.show()