title: Rounding frame_time and smooth transitions for gganimate
body: <p>I have the following data frame:</p>
  
  <pre><code># Seed RNG
  set.seed(33550336)
  
  # Create data frame
  df &lt;- data.frame(x = runif(100), 
                   y = runif(100), 
                   t = runif(100, min = 0, max = 10))
  </code></pre>
  
  <p>I'd like to plot points (i.e., at <code>x</code> and <code>y</code> coordinates) appearing and disappearing as a function of <code>t</code>. <code>gganimate</code> is awesome, so I used that.</p>
  
  <pre><code># Load libraries
  library(gganimate)
  library(ggplot2)
  
  # Create animation
  g &lt;- ggplot(df, aes(x = x, y = y))
  g &lt;- g + geom_point(colour = "#FF3300", shape = 19, size = 5, alpha = 0.25)
  g &lt;- g + labs(title = 'Time: {frame_time}')
  g &lt;- g + transition_time(t)
  g &lt;- g + enter_fade() + exit_fade()
  animate(g, fps = 1)
  </code></pre>
  
  <p>This code produced the following:</p>
  
  <p><a href="https://i.stack.imgur.com/Qzfbi.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Qzfbi.gif" alt="enter image description here"></a></p>
  
  <p>There are a couple of things that I don't like about this. </p>
  
  <ol>
  <li>The transitions are very abrupt. My hope using <code>enter_fade</code> and <code>exit_fade</code> was that the points would fade into view, then back out. Clearly this isn't the case, but how <em>would</em> I achieve this result? </li>
  <li>I would like to round <code>{frame_time}</code>, so that while the points fade in and out at fractions of <code>t</code>, the actual time <code>t</code> that would be shown would be an integer. If <code>frame_time</code> was a regular variable, this would be simple enough using something like <code>bquote</code> and <code>round</code>, but this doesn't seem to be the case. How can I round <code>frame_time</code> in my title? </li>
  </ol>