title: Construct a manual legend for a complicated plot
body: <p>I cannot figure out how to manually set up a legend for this plot. All I really want is a simple legend to the right that uses the three colors and has a name next to each.</p>
  
  <p><img src="https://i.stack.imgur.com/xYukB.png" alt="enter image description here"></p>
  
  <p>The current code looks like this: </p>
  
  <pre><code>a &lt;-c("S1","S2","S3","S4","S5","S6","S7","S8","S9") #names
  b &lt;-c(0.23,0.26,0.55,0.56,0.36,0.23,0.18,0.06,0.04) #mean t0
  c &lt;-c(0.64,0.6,0.81,1.4,0.89,0.55,0.48,0.22,0.09) #mean t1
  d &lt;-c(0.20,0.23,0.52,0.53,0.33,0.20,0.15,0.04,0.03) #SD low t0
  e &lt;-c(0.26,0.29,0.58,.59,0.39,0.26,0.21,0.08,0.05) #SD high t0
  f &lt;-c(0.67,0.63,0.86,1.44,0.93,0.59,0.51,0.25,0.10) #SD high t1
  g &lt;-c(0.61,0.57,0.78,1.36,0.85,0.53,0.45,0.19,0.08) #SD low t1
  h &lt;-c(0.41,0.34,0.26,0.84,0.53,0.32,0.30,0.16,0.05) #absolute change
  
  data &lt;- data.frame(a,b,c,d,e,f,g,h)
  
  ggplot(data=data,aes(a)) + 
    geom_bar(stat="identity", aes(y=h),fill="#62c76b",colour="#333333")+ #green
    geom_line(aes(y=b,group=1),size=1.0,colour="#f04546") +   #red
    geom_point(aes(y=b),size=3, colour="#f04546") +           #red
    geom_errorbar(aes(ymin=d, ymax=e), colour="#f04546", width=0.1, size=.8) + 
    geom_line(aes(y=c,group=1),size=1.0,colour="#3591d1") +   #blue 
    geom_point(aes(y=c),size=3, colour="#3591d1") +           #blue
    geom_errorbar(aes(ymin=f, ymax=g), colour="#3591d1", width=0.1, size=.8) + 
    ylab("Symptom severity") + xlab("PHQ-9 symptoms") +
    ylim(0,1.6) +
    theme_bw() +
    theme(axis.title.x = element_text(size = 15, vjust=-.2)) +
    theme(axis.title.y = element_text(size = 15, vjust=0.3))
  </code></pre>