如何在sklearn中使用datasets.fetch_mldata（）？

Question

我正在尝试运行以下代码以获得简短的机器学习算法：

import re
import argparse
import csv
from collections import Counter
from sklearn import datasets
import sklearn
from sklearn.datasets import fetch_mldata

dataDict = datasets.fetch_mldata('MNIST Original')

在这段代码中，我试图通过sklearn读取mldata.org上的数据集“MNIST Original”。这将导致以下错误（有更多的代码行，但在这一行出现错误）：

Traceback (most recent call last):
  File "C:\Program Files (x86)\JetBrains\PyCharm 2.7.3\helpers\pydev\pydevd.py", line 1481, in <module>
    debugger.run(setup['file'], None, None)
  File "C:\Program Files (x86)\JetBrains\PyCharm 2.7.3\helpers\pydev\pydevd.py", line 1124, in run
    pydev_imports.execfile(file, globals, locals) #execute the script
  File "C:/Users/sony/PycharmProjects/Machine_Learning_Homework1/zeroR.py", line 131, in <module>
    dataDict = datasets.fetch_mldata('MNIST Original')
  File "C:\Anaconda\lib\site-packages\sklearn\datasets\mldata.py", line 157, in fetch_mldata
    matlab_dict = io.loadmat(matlab_file, struct_as_record=True)
  File "C:\Anaconda\lib\site-packages\scipy\io\matlab\mio.py", line 176, in loadmat
    matfile_dict = MR.get_variables(variable_names)
  File "C:\Anaconda\lib\site-packages\scipy\io\matlab\mio5.py", line 294, in get_variables
    res = self.read_var_array(hdr, process)
  File "C:\Anaconda\lib\site-packages\scipy\io\matlab\mio5.py", line 257, in read_var_array
    return self._matrix_reader.array_from_header(header, process)
  File "mio5_utils.pyx", line 624, in scipy.io.matlab.mio5_utils.VarReader5.array_from_header (scipy\io\matlab\mio5_utils.c:5717)
  File "mio5_utils.pyx", line 653, in scipy.io.matlab.mio5_utils.VarReader5.array_from_header (scipy\io\matlab\mio5_utils.c:5147)
  File "mio5_utils.pyx", line 721, in scipy.io.matlab.mio5_utils.VarReader5.read_real_complex (scipy\io\matlab\mio5_utils.c:6134)
  File "mio5_utils.pyx", line 424, in scipy.io.matlab.mio5_utils.VarReader5.read_numeric (scipy\io\matlab\mio5_utils.c:3704)
  File "mio5_utils.pyx", line 360, in scipy.io.matlab.mio5_utils.VarReader5.read_element (scipy\io\matlab\mio5_utils.c:3429)
  File "streams.pyx", line 181, in scipy.io.matlab.streams.FileStream.read_string (scipy\io\matlab\streams.c:2711)
IOError: could not read bytes

我试过上网调查，但几乎没有任何帮助。任何与解决此错误相关的专家帮助将非常感谢。

蒂亚。

Answer 1

我从这个链接下载了数据集

https://github.com/amplab/datascience-sp14/blob/master/lab7/mldata/mnist-original.mat

然后我输入这些行

from sklearn.datasets import fetch_mldata
mnist = fetch_mldata('MNIST original', transpose_data=True, data_home='files')

***路径是（您的工作目录）/files/mldata/mnist-original.mat

我希望你明白，这对我很有用

Answer 2

似乎缓存的数据已损坏。尝试删除它们并再次下载（需要一点时间）。如果没有不同的指定，“MINST original”的数据应该在

~/scikit_learn_data/mldata/mnist-original.mat

Answer 3

从0.20版开始，sklearndeprecatesfetch_mldata函数并改为添加^{}。

使用以下代码下载MNIST dataset：

from sklearn.datasets import fetch_openml
mnist = fetch_openml('mnist_784')

不过，格式有些变化。例如，mnist['target']是一个字符串类别标签数组（不像以前那样浮动）。