title: How to make a field in Kibana numeric (from String)
body: <p>I've inherited an ELK stack for logs and I'm still learning the ropes - I've been tasked with making two fields numeric on a certain type on our logstash indexes. Can't seem to figure out how to do this. Things I tried:</p>
  
  <ol>
  <li>In the Kibana settings page, went to my logstash index and found the field. Went to edit on the controls tab, saw type listed as String (and it was immutable). Dropdown for format shows URL and String.</li>
  <li>Went to one of my Elasticsearch hosts and found the grok rule for the document type, and found that they were indeed written to parse the field as a number. Example: <code>%{NUMBER:response_code}</code></li>
  <li>Ran out of ideas, since I don't know my way around the ELK stack.</li>
  </ol>
  
  <p>Any help greatly appreciated, especially links to relevant documentation so I can understand what's going on. I'd be googling harder if I knew what to google.</p>