title: What does "S3 methods" mean in R?
body: <p>Since I am fairly new to R, I do not know what the S3 methods and objects are. I found that there are S3 and S4 object systems, and some recommend to use S3 over S4 if possible (See Google's R Style Guide at <a href="http://google-styleguide.googlecode.com/svn/trunk/google-r-style.html" rel="noreferrer">http://google-styleguide.googlecode.com/svn/trunk/google-r-style.html</a>)*. However, I do not know the exact definition of S3 methods/objects.</p>
  
  <p>Update: As of 2019, Google's R Style Guide hyperlink is now <a href="https://google.github.io/styleguide/Rguide.html" rel="noreferrer">here</a>.</p>