title: Rename data frame
body: <p>I have a data.frame with name df. I would like to save it in a file with a better name. 
  I would like to be able to do this:</p>
  
  <pre><code>df = ...
  
  rename.data.frame(df, "gdp_2001_2014") 
  
  # Now the data.frame has a new name and can be used as normal:
  gdp_2001_2014$y = 0
  
  # And it can be saved with a nice name:
  save(gdp_2001_2014, file=".\\datafile.Rdata")
  </code></pre>
  
  <p>The name is important of the following reason: when you load data the name follows automatically:</p>
  
  <pre><code>load(".\\datafile.Rdata")
  
  summary(gdp_2001_2014)
  </code></pre>