为什么即使使用相同的参数，readBin（）也会返回不同的值？

Question

我正在使用依赖readBin()的函数将MNIST图像文件读入R。但是，逐行运行该函数，我发现readBin()对于同一行代码返回不同的值（不更改任何参数）。怎么会来？

#Getting the data
> download.file("http://yann.lecun.com/exdb/mnist/t10k-images-idx3-ubyte.gz",
+               "t10k-images-idx3-ubyte.gz")

#unzipped the .gz file manually out of R. The extracted file is 'train-images.idx3-ubyte'

#Using file() to read the 'train-images.idx3-ubyte' file
> f = file("train-images.idx3-ubyte", 'rb')

#this is what 'f' is:
> f
A connection with                                     
description "train-images.idx3-ubyte"
class       "file"                   
mode        "rb"                     
text        "binary"                 
opened      "opened"                 
can read    "yes"                    
can write   "no" 

#The following lines show the execution of readBin with the same parameters, though giving a different value each time

> readBin(f, 'integer', n = 1, size = 4, endian = 'big')
[1] 2051
> readBin(f, 'integer', n = 1, size = 4, endian = 'big')
[1] 60000
> readBin(f, 'integer', n = 1, size = 4, endian = 'big')
[1] 28
> readBin(f, 'integer', n = 1, size = 4, endian = 'big')
[1] 28
> readBin(f, 'integer', n = 1, size = 4, endian = 'big')
[1] 0

Answer 1

您打开file连接，然后再关闭它。因此，结果就是您所经历的。您只需阅读下一个号码即可。

重复序列

• 打开连接
• readBin
• 关闭连接

将为您提供一致的结果。

或者也使用readBin("the_file__not_the_connection", 'integer', n = 1, size = 4, endian = 'big')。