隔离林值的长度与索引的长度不匹配

Question

我正在运行隔离林，试图将其应用于 10049972 行 x 19 列的数据库，但运行 2 小时后出现以下错误。我真的不明白为什么会得到它，也不知道如何解决？

代码：

 import numpy as np

import pandas as pd

import matplotlib.pyplot as plt

%matplotlib inline

from sklearn.ensemble import IsolationForest


df = pd.read_csv('D:\\Project\\database\\4-Final\\Final After.csv',low_memory=True)


iForest = IsolationForest(behaviour='new', n_estimators=80,  contamination='auto' , max_samples=150)


df['anomaly'] = iForest.fit_predict(df.values.reshape(-1,1))


df=df.drop(df['anomaly'==-1],inplace=True)

df.to_csv('D:\\Project\\database\\4-Final\\IF TEST.csv', index=False)

错误是：

 ValueError                                Traceback (most recent call last)
<ipython-input-1-fc55c8b1f328> in <module>
     16 
     17 
---> 18 df['anomaly'] = iForest.fit_predict(df.values.reshape(-1,1))
     19 
     20 

C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\frame.py in __setitem__(self, key, value)
   3368         else:
   3369             # set column
-> 3370             self._set_item(key, value)
   3371 
   3372     def _setitem_slice(self, key, value):

C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\frame.py in _set_item(self, key, value)
   3443 
   3444         self._ensure_valid_index(value)
-> 3445         value = self._sanitize_column(key, value)
   3446         NDFrame._set_item(self, key, value)
   3447 

C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\frame.py in _sanitize_column(self, key, value, broadcast)
   3628 
   3629             # turn me into an ndarray
-> 3630             value = sanitize_index(value, self.index, copy=False)
   3631             if not isinstance(value, (np.ndarray, Index)):
   3632                 if isinstance(value, list) and len(value) > 0:

C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\internals\construction.py in sanitize_index(data, index, copy)
    517 
    518     if len(data) != len(index):
--> 519         raise ValueError('Length of values does not match length of index')
    520 
    521     if isinstance(data, ABCIndexClass) and not copy:

ValueError: Length of values does not match length of index 

谢谢。

Answer 1

我认为问题可能出在

df.values.reshape(-1,1)

看看这个例子

df = pd.DataFrame([(.2, .3), (.0, .6), (.6, .0), (.2, .1)], columns=['dogs', 'cats'])

df
   dogs  cats
0   0.2   0.3
1   0.0   0.6
2   0.6   0.0
3   0.2   0.1

df.values.reshape(-1,1)
array([[0.2],
       [0.3],
       [0. ],
       [0.6],
       [0.6],
       [0. ],
       [0.2],
       [0.1]])

因此，您最终为fit_predict 提供了一个shape (n_samples*n_feature, 1) 向量，并且您将生成的shape (n_samples*n_feature,) 作为一列插入到带有shape (n_samples,n_feature) 的df。行数不匹配。