如何在R语言中展现用户和环境变量？ [英] How to unfold user and environment variable in R language?

问题描述

例如，在Python中，您可以通过写出以下代码来获取它：

有没有办法在R中扩展波浪符号和环境变量？

  import os 
 os.path.expanduser（〜/ r_workspace）＃return/ Users / yourname / r_workspace（在OS X中）
 os.path.expandvars（$ R）＃return/ Users / yourname / r_workspace，如果您提前设置$ R
  

R是否提供了这种功能？我不喜欢写下面的代码：

  read.csv（/ Users / myname / python_workspace / subdirectory_1 /subdirectory_2/data.csv）
  




解决方案

相同！

  path.expand（〜）
＃[1]/ Users / Simon
  

path.expand 将通过替换用户主目录（如果在该平台上定义）的主要波浪号。

和 Sys.getenv（）获取系统中定义的环境变量的值，例如

 ＃R主目录的路径
 Sys.getenv （R_HOME）
＃[1]/Library/Frameworks/R.framework/Resources
 
＃默认路径R库
 Sys.getenv（R_LIBS ）
＃[1]〜/ R64Libs
  

查看可用的环境变量。 ..

$ b

  head（names（Sys.getenv（）））
＃[1]__CF_USER_TEX $ _ 
 
 
 
 $ b $$$$$$ b 
定义新的环境变量
 
 
 
要设置环境变量以使其始终可用于R，您需要将该变量设置为名为 .Renviron 默认情况下，它位于您的 {$ HOME} 目录中。因此，例如要使环境变量 R_WORKSPACE 可用添加行
  R_WORKSPACE =〜/ Documents / R / StackOverflow 
  
至 / Users / Simon /.Renivron 。然后当我加载R时，您会看到路径扩展自动完成... 
 ＃清洁工作区 - 注释掉，所以你不要擦你的会话！ 
＃rm（list = ls（））
 
＃看到这个变量现在可以在R 
 Sys.getenv（R_WORKSPACE）
 [1] 〜/ Documents / R / StackOverflow
  
请参阅回答这里了解更多信息和选项。
 
Are there any ways to expand tilde and environment variables in R?

For example, in Python, you can get it by writing out the following set of codes:
import os
os.path.expanduser("~/r_workspace") # return "/Users/yourname/r_workspace" (in OS X)
os.path.expandvars("$R") # return "/Users/yourname/r_workspace", if you set "$R" to it in advance
Does R provide the sort of functions? I don't like to bother to write the following code:
read.csv("/Users/myname/python_workspace/subdirectory_1/subdirectory_2/data.csv")

解决方案
Pretty much the same!
path.expand("~")
#[1] "/Users/Simon"
path.expand will expand a path name by replacing a leading tilde by the user's home directory (if defined on that platform).

And Sys.getenv() to get the value of environmental variables defined on your system, e.g.
#  Path to R home directory
Sys.getenv( "R_HOME" )
#[1] "/Library/Frameworks/R.framework/Resources"

# Path to default R library
Sys.getenv("R_LIBS")
#[1] "~/R64Libs"
To see the available environment variables...
head( names(Sys.getenv()) )
#[1] "__CF_USER_TEXT_ENCODING"    "Apple_PubSub_Socket_Render" "Apple_Ubiquity_Message"    
#[4] "COMMAND_MODE"               "DISPLAY"                    "EDITOR"    


Defining a new environmental variable

To set an environment variable to make it always available to R you need to set that variable in a file called .Renviron which by default is located in your {$HOME} directory. So for instance to make the environment variable R_WORKSPACE available I add the line
R_WORKSPACE = ~/Documents/R/StackOverflow
To /Users/Simon/.Renivron. Then when I load up R you see that path expansion is done automatically...
#  Clean workspace - commented out so you don't wipe your session!
#  rm( list = ls() )

#  See that variable is now available in R
Sys.getenv( "R_WORKSPACE" )
[1] "~/Documents/R/StackOverflow"
See the answer here for a bit more info and options.

                        
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