title: ggplot2 - How to set legend for geom_ribbon, geom_line and geom_point with the same color
body: <p>I have a plot that includes geom_ribbon, geom_line and geom_point with the same color. Could you please tell me how I can set a legend that includes descriptions for all 3 types and also considers the alpha values?</p>
  
  <p>Code: </p>
  
  <pre><code>predplot &lt;- ggplot(data=AllData, aes(x = Date)) +
    geom_ribbon(aes(ymin=AllData$advancedFitLower95, ymax=AllData$advancedFitUpper95, fill="red"), alpha=0.4) +
    geom_ribbon(aes(ymin=AllData$advancedFitLower80, ymax=AllData$advancedFitUpper80, fill="red"), alpha=0.7) +
    geom_line(aes(y = AllData$advancedFitForecast), colour = "red") +
    geom_point(aes(y = AllData$Destatis), shape=21, fill="white", colour = "red", size=2, stroke=2) +
    scale_x_date(date_breaks = "1 year", date_labels = "%Y") +
    labs(x="", 
         y= "births") + 
    theme(axis.title=element_text(size=11),
          axis.text=element_text(size=11, colour = "black"),
          legend.title = element_text(size=11),
          legend.text = element_text(size=11))
  
  plot(predplot)
  </code></pre>
  
  <p>Screenshot: <a href="https://i.stack.imgur.com/yt2VE.png" rel="nofollow noreferrer">Plot</a></p>
  
  <p>Sample Data:</p>
  
  <pre><code>structure(list(Date = structure(c(14488, 14518, 14549, 14579, 
  14610, 14641, 14669, 14700, 14730, 14761, 14791), class = "Date"), 
      Destatis = c(59612, 54760, 51319, 53869, 55273, 50314, 55486, 
      52020, 56054, 57531, 61918), Google = c(43, 43, 42, 36, 42, 
      42, 38, 38, 36, 36, 37), baseFitForecast = c(59271.9941102255, 
      56055.8996704734, 51255.5683820705, 52555.810279121, 55472.8442207511, 
      50398.5498216408, 53384.0684325976, 51442.6744082598, 54315.656143645, 
      55958.488805051, 60578.2928236282), advancedFitForecast = c(59858.2784132212, 
      56532.8381467247, 52011.5910887163, 53545.5662783686, 55911.0730077498, 
      51096.7453713563, 54158.6688635223, 52311.8612991644, 55214.1783090307, 
      56753.0170022236, 61474.9182990983), advancedFitLower80 = c(57654.4066959064, 
      54356.5696860696, 49851.5946301954, 51409.5599195636, 53771.2991570756, 
      48985.3271962111, 52070.5287242434, 50228.384597234, 53153.27240174, 
      54699.1820518215, 59444.5589990337), advancedFitLower95 = c(56487.7474813286, 
      53204.5227529061, 48708.1615746366, 50278.8264556699, 52638.5713034585, 
      47867.6099304977, 50965.1341063625, 49125.4586539642, 52062.2947154126, 
      53611.9475039649, 58369.7517097918), advancedFitUpper80 = c(62062.150130536, 
      58709.1066073798, 54171.5875472373, 55681.5726371735, 58050.8468584239, 
      53208.1635465015, 56246.8090028013, 54395.3380010947, 57275.0842163213, 
      58806.8519526258, 63505.2775991629), advancedFitUpper95 = c(63228.8093451138, 
      59861.1535405433, 55315.020602796, 56812.3061010672, 59183.574712041, 
      54325.8808122149, 57352.2036206821, 55498.2639443645, 58366.0619026487, 
      59894.0865004823, 64580.0848884049)), .Names = c("Date", 
  "Destatis", "Google", "baseFitForecast", "advancedFitForecast", 
  "advancedFitLower80", "advancedFitLower95", "advancedFitUpper80", 
  "advancedFitUpper95"), row.names = 69:79, class = "data.frame")
  </code></pre>