title: Plot time series and forecast simultaneously using ggplot2
body: <p>I have a time series with forecast and confidence interval data, I wanted to plot them simultaneously using ggplot2. I'm doing it by the code below:</p>
  
  <pre><code>set.seed(321)
  library(ggplot2)
  #create some dummy  data similar to mine
  
  sample&lt;-rnorm(350)
  forecast&lt;-rnorm(24)
  upper&lt;-forecast+2*sd(forecast)
  lower&lt;-forecast-2*sd(forecast)
  
  
  ## wrap data into a data.frame
  df1 = data.frame(time = seq(325,350,length=26), M = sample[325:350], isin = "observations")
  df2 = data.frame(time = seq(351,374,length=24), M = forecast , isin = "my_forecast")
  df3 = data.frame(time = seq(351,374,length=24), M = upper ,isin = "upper_bound")
  df4 = data.frame(time = seq(351,374,length=24), M = lower, isin = "lower_bound")
  df = rbind(df1, df2, df3, df4)
  
  ## ggplot object 
  ggplot(df, aes(x = time, y = M, color = isin)) + geom_line()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/0H6Nk.png" alt="enter image description here"></p>
  
  <p>How can I join upper and lower lines in one color? and also how can I set specific colors to forecast and sample?</p>