title: R, ggplot2: Fit curve to scatter plot
body: <p>I am trying to fit curves to the following scatter plot with ggplot2.</p>
  
  <p>I found the geom_smooth function, but trying different methods and spans, I never seem to get the curves right...</p>
  
  <p>This is my scatter plot:
  <a href="https://i.stack.imgur.com/gHzQw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gHzQw.png" alt="test1"></a></p>
  
  <p>And this is my best attempt:
  <a href="https://i.stack.imgur.com/kPwMl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kPwMl.png" alt="test2"></a></p>
  
  <p>Can anyone get better curves that fit correctly and don't look so wiggly? Thanks!</p>
  
  <p>Find a MWE below:</p>
  
  <pre><code>my.df &lt;- data.frame(sample=paste("samp",1:60,sep=""),
                      reads=c(523, 536, 1046, 1071, 2092, 2142, 4184, 4283, 8367, 8566, 16734, 17132, 33467, 34264, 66934, 68528, 133867, 137056, 267733, 274112, 409, 439, 818, 877, 1635, 1754, 3269, 3508, 6538, 7015, 13075, 14030, 26149, 28060, 52297, 56120, 104594, 112240, 209188, 224479, 374, 463, 748, 925, 1496, 1850, 2991, 3699, 5982, 7397, 11963, 14794, 23925, 29587, 47850, 59174, 95699, 118347, 191397, 236694),
                      number=c(17, 14, 51, 45, 136, 130, 326, 333, 742, 738, 1637, 1654, 3472, 3619, 7035, 7444, 13133, 13713, 21167, 21535, 11, 22, 30, 44, 108, 137, 292, 349, 739, 853, 1605, 1832, 3099, 3565, 5287, 5910, 7832, 8583, 10429, 11240, 21, 43, 82, 124, 208, 296, 421, 568, 753, 908, 1127, 1281, 1448, 1608, 1723, 1854, 1964, 2064, 2156, 2259),
                      condition=rep(paste("cond",1:3,sep=""), each=20))
  
  png(filename="TEST1.png", height=800, width=1000)
  print(#or ggsave()
  ggplot(data=my.df, aes(x=reads, y=log2(number+1), group=condition, color=condition)) +
      geom_point()
  )
  dev.off()
  
  png(filename="TEST2.png", height=800, width=1000)
  print(#or ggsave()
  ggplot(data=my.df, aes(x=reads, y=log2(number+1), group=condition, color=condition)) +
      geom_point() +
      geom_smooth(se=FALSE, method="loess", span=0.5)
  )
  dev.off()
  </code></pre>