title: How to plot a subset of a data frame in R?
body: <p>Is there a simple way to do this in R: </p>
  
  <pre><code>plot(var1,var2, for all observations in the data frame where var3 &lt; 155)
  </code></pre>
  
  <p>It is possible by creating a new data  <code>newdata &lt;- data[which( data$var3 &lt; 155),]</code> but then I have to redefine all the variables <code>newvar1 &lt;- newdata$var1</code> etc.</p>