title: ggplot2: how do I add a second plot line
body: <p>Ok,
  [R3.4.2 + ggplot2]
  Using the data example listed below, how do I add a second data plot? I tried this example which I found on this site;</p>
  
  <pre><code>library(ggplot2]
  ** This is part of the origanl code ****
  rpt&lt;-read.csv(file="rpt.csv,header=T)
  rpt1&lt;-read.csv(file="rpt1.csv,header=T)
  *** code starts here *****
  ggplot(rpt,aes(JulianDate,w)) + geom_line(aes(color="First   line")) +
               geom_line(data=rpt1, aes(color="Second line")) + labs(color="Legend text")
  </code></pre>
  
  <p>The first plot has x=rpt$JulianDate, y=rpt1$w; and the second plot has x1= rpt1$JDAy and y2=rpt1$wolf)</p>
  
  <p>The data (use dget(_) to read it):</p>
  
  <pre><code>structure(list(
  JDay = c(57023, 57024, 57027, 57028, 57029, 57031, 57032, 57035, 57037),
  Obs = c(1, 1, 1, 1, 1, 1, 1, 1, 1),
  w = c(71, 105, 64, 44, 45, 38, 66, 49, 28),
  WStd = c(0, 0, 0, 0, 0, 0, 0, 0, 0),
  wolf = c(91.59, 135.45, 82.56, 56.76, 58.05, 49.02, 85.14, 63.21, 36.12),
  Adj = c(0, 0, 0, 0, 0, 0, 0, 0, 0)),
  .Names = c("JDay", "Obs", "w", "WStd", "wolf", "Adj"),
  class = "data.frame",
  row.names =  c(NA, -9L))
  </code></pre>