title: In R, using melt(), how can I hide warning messages?
body: <p>I'm melting some data and don't want to provide an id.var parameter to melt.  The data melts fine, but I get the </p>
  
  <pre><code>"No id variables; using all as measure variables"
  </code></pre>
  
  <p>Is there a way to prevent that message from coming up, or a way to say id.var=default or something like that? An iris example using dplyr:</p>
  
  <pre><code>&gt; dt &lt;- iris %&gt;% summarize_at(c("Sepal.Length","Sepal.Width"), funs(mean))
  &gt; dt
    Sepal.Length Sepal.Width
  1     5.843333    3.057333
  &gt; melt(dt, value.name="Mean")
  No id variables; using all as measure variables
        variable     Mean
  1 Sepal.Length 5.843333
  2  Sepal.Width 3.057333
  </code></pre>
  
  <p>Alternatively is there a way to tell a function to not print warning messages or something like that?  Thanks!</p>