text: user9995: I have a protein refseq (eg, NP_000029). How can I get the corresponding gene ID (ag, APC) from NCBI using an R package?
  
  user9693: You can do this with the reutils package, which provides an API to NCBI's E-utilities. Here's an example for your specific question:
  install.packages("reutils")
  library(reutils)
  
  # Get universal identifier
  uid <- esearch("NP_000029", db = "gene")
  # Fetch summary
  sm <- esummary(uid, db = "gene")
  # Extract specific tag
  sm$xmlValue("//Name")
  
  
original_text: 9995: <p>I have a protein refseq (eg, NP_000029). How can I get the corresponding gene ID (ag, APC) from NCBI using an R package?</p>
   9693: <p>You can do this with the <a href="https://github.com/gschofl/reutils" rel="nofollow noreferrer">reutils</a> package, which provides an API to NCBI's <a href="https://www.ncbi.nlm.nih.gov/books/NBK25500/" rel="nofollow noreferrer">E-utilities</a>. Here's an example for your specific question:</p>
  <pre class="lang-r prettyprint-override"><code>install.packages(&quot;reutils&quot;)
  library(reutils)
  
  # Get universal identifier
  uid &lt;- esearch(&quot;NP_000029&quot;, db = &quot;gene&quot;)
  # Fetch summary
  sm &lt;- esummary(uid, db = &quot;gene&quot;)
  # Extract specific tag
  sm$xmlValue(&quot;//Name&quot;)
  </code></pre>
  