title: R Scale plot elements within PDF of set width and height
body: <p>Though R plots sent to a PDF can be rescaled at will in an illustration or page layout software, scientific journals often insist that the plots provided have specific dimensions.</p>
  
  <p>Can the size of all plotting elements be scaled within a given PDF size directly in R?</p>
  
  <pre><code>require(ggplot2)
  
  p &lt;- qplot(data=iris,
             x=Petal.Width,
             y=Petal.Length,
             colour=Species)
  
  pdf("./test_plot_default.pdf")
  print(p)
  graphics.off()
  </code></pre>
  
  <p>Produces adequate scaling of plot elements</p>
  
  <p><img src="https://i.stack.imgur.com/RZivO.jpg" alt="test plot with default pdf size"></p>
  
  <p>However, changing PDF size elements does not cause the plot elements to scale.  With smaller PDFs, the plotting elements are overly enlarged compared to the plotting space.</p>
  
  <pre><code>pdf("./test_plot_dimentionsions required by journal.pdf", width=3, height=3)
  print(p)
  graphics.off()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/5AGdi.jpg" alt="enter image description here"></p>
  
  <p>Using @Rosen Matev suggestion:</p>
  
  <pre><code>update_geom_default("point", list(size=1))
  theme_set(theme_grey(base_size=6))
  pdf("./test_plot_dimentionsions required by journal.pdf", width=3, height=3)
  print(p)
  graphics.off()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/LDJ69.jpg" alt="enter image description here"></p>