title: How to substitute variable in file path
body: <p>I know nothing about R, but would like to know to substitute a variable that could be used to replace the <code>/home/subdirectory/DataFiles/</code> in the following (snippet) of R code:</p>
  
  <pre><code>x1 &lt;- subset(read.csv("/home/subdirectory/DataFiles/Isic_bilateral_trade1.csv"),
               year&gt;=1990)
  </code></pre>