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阅读mldata.org上的数据集"MNIST Original".这导致以下错误(有更多的代码行,但我在此特定行收到错误):

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

我曾尝试过在互联网上进行研究,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不胜感激.

TIA.

Answer 1

看起来缓存的数据已损坏.尝试删除它们并再次下载(需要一点时间).如果没有另外指定,则"MINST original"的数据应为

~/scikit_learn_data/mldata/mnist-original.mat

Answer 2

从0.20版开始，sklearn 弃用 fetch_mldata函数，fetch_openml而是添加了。

使用以下代码下载MNIST数据集：

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

格式有所更改。例如，mnist['target']是一个字符串类别标签的数组（不像以前那样浮动）。

Answer 3

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

然后我输入了这些行

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，它对我很有效

Answer 4

这就是“MNIST 原创”。“o”上有小写字母。