machine-learning - 機械学習データの代入時に疑問符（'？'）を NaN に変換するエラー

Question

すべての欠落データ (「?」で示される) をNaN代入し、代入ツールを使用してsklearnそれらを平均値に平均化しようとしています。私の問題を再現できるように、以下のコードを含めました。PyCharm を IDE、Mac OS X、および Py 2.7.12 で anaconda として使用します。

これは私のコードです:

import matplotlib.pyplot as plt
import numpy as np
import pandas as pd
df = pd.read_csv('http://archive.ics.uci.edu/ml/machine-learning-databases/communities/communities.data', header=None, sep=',\s', na_values=["?"])
df.tail()
from sklearn.preprocessing import Imputer
imr = Imputer(missing_values='NaN', strategy='mean', axis=0)
imr= imr.fit(df)

そして、ここに私のエラーメッセージがあります

 /Users/zdong/anaconda/bin/python/Users/zdong/PycharmProjects/ml/crim_workingfile.py

/Users/zdong/PycharmProjects/ml/crim_workingfile.py:4: ParserWarning:   Falling back to the 'python' engine because the 'c' engine does not support regex separators (separators > 1 char and different from '\s+' are interpreted as regex); you can avoid this warning by specifying engine='python'.

df = pd.read_csv('http://archive.ics.uci.edu/ml/machine-learning databases/communities/communities.data', header=None, sep=',\s', na_values=["?"])

Traceback (most recent call last):
  File "/Users/zdong/PycharmProjects/535_final/535_workingfile.py", line 8,
in <module>
imr= imr.fit(df)
  File "/Users/zdong/anaconda/lib/python2.7/site-packages/sklearn/preprocessing/imputation.py",
line 156, in fit
force_all_finite=False)
  File "/Users/zdong/anaconda/lib/python2.7/site-packages/sklearn/utils/validation.py"
line 382, in check_array
array = np.array(array, dtype=dtype, order=order, copy=copy)
ValueError: invalid literal for float(): 6,?,?,Ontariocity,10,0.2,0.78,0.14,0.46,0.24,0.77,0.5,0.62,0.4,0.17,0.21,1,0.4,0.73,0.22,0.25,0.26,0.47,0.29,0.36,0.24,0.28,0.32,0.22,0.27,0.25,0.29,0.16,0.35,0.5,0.55,0.16,0.47,0.58,0.53,0.2,0.6,0.24

打ちのめされた初心者QAQを助けてください...