title: R on Windows - compile errors - \U used without Hex digits
body: <p>hoping someone can help me.</p>
  
  <p>I have R 3.2.2 (2015-08-14) and RStudio 0.99.489
  on Windows 7.
  my default working directory is c:\users\adamsben\, but could be anywhere.</p>
  
  <p>I know that when I load a file, such as
  <code>read.csv("c:\users\adamsben\data.csv")</code>
  I'll get an error.  </p>
  
  <p>Instead I know I need to write:
      <code>read.csv("c:\\users\\adamsben\\data.csv")</code>
      or
      <code>read.csv("c:/users/adamsben/data.csv")</code></p>
  
  <p>However, I'm getting the same error when I try to compile source code or try to use <code>knitr.</code></p>
  
  <p>The error I get is: </p>
  
  <p><code>Error: '\U' used without hex digits in character string starting "'C:\U"
  Execution halted</code></p>
  
  <p>Obviously, the error is related to c:\Users\ but now I'm not sure how to fix.  I tried changing my working directory, no dice.</p>
  
  <p>Also, I've tried searching for this error on both stackoverflow and google generally, and all I get are people trying to read in data files and needing to change to <code>\\</code> or <code>/</code></p>
  
  <p>An example:
  trying to install shiny
      devtools::install_github('rstudio/shinyapps')</p>
  
  <pre><code>Downloading GitHub repo rstudio/shinyapps@master
  Installing shinyapps
  "C:/PROGRA~1/R/R-32~1.2/bin/x64/R" --no-site-file  \
    --no-environ --no-save --no-restore CMD INSTALL  \
  "C:/Users/adamsben/AppData/Local/Temp/RtmpIJ5NwN/devtools19c84a7c5e0b
  /rstudio-shinyapps-688a4ac"  \
  --library="C:/Users/adamsben/Documents/R/win-library/3.2"  \
  --install-tests 
  
  Error: '\U' used without hex digits in character string starting "'C:\U"
  Execution halted
  </code></pre>
  
  <p>I really have no idea how to fix something embedded in someone else's code.
  Any ideas?</p>