R：在Linux上的readBin和writeBin [英] R: readBin and writeBin on linux

问题描述

我想以二进制格式写入（以后检索）数据。我试图得到一个最小的例子，至少到嗅觉测试的水平（读输入应该看起来像书面的输出），但我没有得到它，一贯的权利。我的机器是一个小端的linux，但是由于这里是不变的，所以我从通话中省略了。我也不确定在写入中指定 size 参数是更好还是省略。无论如何，加载的输入看起来不像 out ：

  out< -seq（1,50,2）
 
 ## write 
 write< -file（'〜/ output.txt'，'wb'）
 writeBin out，con = write，size = 4）
 close（write）
 
 ## read 
 read< -file（'〜/ output.txt'，'rb'） 
 readBin（con = read，what = numeric（），n = length（out））
＃[1] 3.200001e + 01 3.276801e + 04 1.048576e + 06 1.677722e + 07 1.006633e + 08 4.026532e + 08 1.610613e + 09 6.442452e + 09 1.503239e + 10 3.006478e + 10 6.012955e + 10 1.202591e + 11 
接近（读）
  

解决方案

这是一个有效的例子：

  R> dat<  -  seq（1,50,2）
 R> dat 
 [1] 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 
 R> 
  

我们只是将对象写入二进制连接 - 省略了第三个参数：

  R> con<  -  file（/ tmp / foo.bin，wb）
 R> writeBin（dat，con）
 R> close（con）
 R> 
  

然后可以读回：

  R> con<  -  file（/ tmp / foo.bin，rb）
 R> dat2<  -  readBin（con，what =numeric，n = length（dat））
 R> dat2 
 [1] 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 
 R> 
 R> all.equal（dat，dat2）
 [1] TRUE 
  

但是，您需要存储长度。我已经使用了一个内部文件格式，它首先写入关于行，列，格式号的固定（已知）数的整数，然后读取/写入总共行*列数值。我们也把这个包装成gzip-ed文件连接。

你甚至可以把它推广到像数据框一样写列 - 但是如果R是你唯一的读者/编写者然后通过 save（）已经存在的序列化更好。

I want to write (and later retrieve) data in binary format. I am trying to get a minimal example to work at least to the level of the smell test (read input should look like written output), but I haven't gotten it just, and consistently right. My machine is a linux with little endian, but since that is constant here, I ommitted it from the calls. I was also not sure if it was better to specify the size argument in the write, or leave it out. At any rate, the loaded input doesn't look like out:

out<-seq(1,50,2)

##write
write<-file('~/output.txt','wb')
writeBin(out,con=write,size=4)
close(write)

##read
read<-file('~/output.txt','rb')
readBin(con=read,what=numeric(),n=length(out))
# [1] 3.200001e+01 3.276801e+04 1.048576e+06 1.677722e+07 1.006633e+08 4.026532e+08     1.610613e+09 6.442452e+09 1.503239e+10 3.006478e+10 6.012955e+10 1.202591e+11
close(read)

解决方案

Here is a worked example:

R> dat <- seq(1,50,2)
R> dat
 [1]  1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
R> 

We just write the object to a binary connection -- omitting your third parameter:

R> con <- file("/tmp/foo.bin", "wb")
R> writeBin(dat, con)
R> close(con)
R> 

And can then read back:

R> con <- file("/tmp/foo.bin", "rb")
R> dat2 <- readBin(con, what="numeric", n=length(dat))
R> dat2
 [1]  1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
R>
R> all.equal(dat, dat2)
[1] TRUE

However, you need to store the length. I have used an internal file format which first writes a fixed (known) number of integers about rows, cols, "format number", ... and then read / writes a total of rows * cols numerics. We also wraps this into a gzip-ed file connection.

You could even generalize this to writing columns as in a data frame -- but if R is your only reader / writer then the already exisiting serialization via save() is better.

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