title: How to fit a smooth curve on a plot with very few points in R
body: <p>I have just 4 data points:</p>
  
  <pre><code>points = c(60, 46, 46, 60)
  </code></pre>
  
  <p>that "want" to describe a parabola. Evidently, though, I can't find a way to make it smooth; instead, I end up with the boxy plot in red below using code along these lines:</p>
  
  <pre><code>plot(points, ylim=c(40,60), pch = 20, col = 2, cex = 2)
  fit = loess(points ~ c(1:4), bw=nrd0, na.rm=T)
  lines(predict(fit), lwd=2, col= 2)
  </code></pre>
  
  <p>I wonder if there is any way of making the corners smooth, so that it looks more like the blue line...</p>
  
  <p><a href="https://i.stack.imgur.com/Ed6Q0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Ed6Q0.png" alt="enter image description here"></a></p>