title: ggplot2 sourcing error: X11 library is missing
body: <p>I'm trying to load ggplot2 library for R.</p>
  
  <p>1) I've installed ggplot2 by this command. It was installed with no errors</p>
  
  <pre><code>install.packages('ggplot2', dependencies = TRUE)
  </code></pre>
  
  <p>2) Then i'm trying to use </p>
  
  <pre><code>library(ggplot2)
  </code></pre>
  
  <p>and get an error</p>
  
  <blockquote>
    <p>Error : .onLoad не удалось в loadNamespace() для 'tcltk', подробности:
    вызов: fun(libname, pkgname)   ошибка: X11 library is missing: install
    XQuartz from xquartz.macosforge.org Ошибка: не удалась загрузка пакета
    или пространства имен для ‘ggplot2’</p>
  </blockquote>
  
  <p>3) Now i try to install XQuartz library by </p>
  
  <pre><code>install.packages("XQuartz")
  </code></pre>
  
  <p>and get this</p>
  
  <blockquote>
    <p>Warning in install.packages :   package ‘XQuartz’ is not available
    (for R version 3.1.2)</p>
  </blockquote>
  
  <p>My R version 3.1.2
  OS X Yosemite 10.10.2</p>
  
  <p>Can you help me in installing ggplot2 pls?</p>