title: Adding mean and sd to spaghetti plot in ggplot
body: <p>I have made a spaghetti plot from this data</p>
  
  <pre><code>head(df)
         x   id stage
  1: 35.15 1001     3
  2: 17.22 1002     5
  3: 24.69 1003     1
  4: 24.88 1004     1
  5: 38.00 1004     5
  6: 24.08 1005     1
  dput(df)
  structure(list(x = c(35.15, 17.22, 24.69, 24.88, 38, 24.08, 23.26, 
  17.8, 19.35, 24.16, 15.76, 18.27, 21.14, 19.2, 18.06, 20.1, 14.05, 
  16.1, 13.77, 12.78, 12.22, 15.42, 12.66, 12.49, 12.31, 12.23, 
  24.75, 22.68, 18.99, 28.32, 18.01, 18.98, 23.12, 31.07, 19.68, 
  27.79, 25.06, 21.46, 9.14, 14.86, 14.05, 8.62, 23.37, 11.46, 
  14.6, 14.07, 9.37, 20.29, 20.18, 18.85, 18.7, 24.02, 17.13, 21.35, 
  21.02, 14.13, 17.48, 15.16, 23.29, 25.44, 19.96, 18.56, 27.85, 
  29.08, 23.1, 23.39, 18.28, 25.96, 19.59, 18.71, 28, 34.28, 26.41, 
  26.87, 24.54, 18.54, 20.75, 25.82, 25.84, 18.35, 20.6, 25.74, 
  19.37, 21.12, 23.06, 15.58, 24.53, 22.65, 16.65), id = c("1001", 
  "1002", "1003", "1004", "1004", "1005", "1005", "1005", "1006", 
  "1006", "1006", "1006", "1007", "1007", "1007", "1007", "1008", 
  "1008", "1009", "1009", "1010", "1010", "1011", "1011", "1011", 
  "1011", "1012", "1012", "1012", "1013", "1013", "1013", "1013", 
  "1014", "1014", "1015", "1015", "1015", "1016", "1016", "1016", 
  "1016", "1017", "1018", "1018", "1018", "1018", "1019", "1019", 
  "1019", "1019", "1020", "1020", "1020", "1020", "1021", "1021", 
  "1022", "1022", "1022", "1022", "1023", "1023", "1024", "1024", 
  "1024", "1025", "1025", "1025", "1025", "1026", "1026", "1026", 
  "1026", "1027", "1027", "1027", "1027", "1028", "1028", "1028", 
  "1028", "1029", "1029", "1029", "1029", "1030", "1030", "1030"
  ), stage = c("3", "5", "1", "1", "5", "1", "2", "5", "1", "2", 
  "3", "5", "1", "2", "3", "5", "1", "5", "1", "5", "1", "5", "1", 
  "2", "3", "5", "1", "2", "5", "1", "2", "3", "5", "5", "5", "1", 
  "2", "5", "1", "2", "3", "5", "5", "1", "2", "3", "5", "1", "2", 
  "3", "5", "1", "2", "3", "5", "1", "5", "1", "2", "3", "5", "3", 
  "5", "2", "3", "5", "1", "2", "3", "5", "1", "2", "3", "5", "1", 
  "2", "3", "5", "1", "2", "3", "5", "1", "2", "3", "5", "1", "2", 
  "5")), class = c("data.table", "data.frame"), row.names = c(NA, 
  -89L), .internal.selfref = &lt;pointer: 0x00000000003d0788&gt;, .Names = c("x", 
  "id", "stage"))
  
  gg.spaghetti_x&lt;-ggplot(df, aes (x = stage, y = x, group = id, color = id))
  gg.spaghetti_x &lt;-gg.spaghetti_x + geom_line() + geom_point() + ylab("X") + stat_summary(fun.y=mean,geom="line",lwd=2,aes(group=1))
  gg.spaghetti_x
  </code></pre>
  
  <p>This gives me a spaghetti plot with a mean, but how do I add sd error bars at each stage? 
  Still keeping all the individiual lines. I tried using stat_summary(fun.y=mean_sd) but that did not work.
  spaghetti plot 
  <a href="https://i.stack.imgur.com/llhaw.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/llhaw.jpg" alt="enter image description here"></a></p>