title: How to import an R function from another package such that it would be available for the user?
body: <p>I am writing a R package and I want to import generic function <code>forecast</code> from the package <strong>forecast</strong>. My package provides the method <code>forecast.myobj</code>. I have the  <code>forecast</code> in the <code>Imports:</code> in the package <code>DESCRIPTION</code> file and my function definition is as following:</p>
  
  <pre><code>##' @export
  forecast.myobj &lt;- function(x) {
  
  }
  </code></pre>
  
  <p>I am using <strong>devtools</strong>  package (version 1.5) to build the package. The generated <code>NAMESPACE</code> has the following</p>
  
  <pre><code>S3method(forecast, myobj)
  importFrom(forecast, forecast)
  </code></pre>
  
  <p>However when I load my package in a clean R session, function <code>forecast</code> is not available. Interestingly though I can see help pages of <code>forecast</code> and <code>forecast.myobj</code> and I can access these functions via <code>forecast::forecast</code> and <code>mypackage:::forecast.myobj</code>. Is it possible somehow to make <code>forecast</code> available to the user without depending on the package <code>forecast</code>? I checked documentation and reviewed a bunch of similar questions here, but I did not find the definite negative or positive answer.</p>