I realize this is probably a simple issue, but I cannot figure out why ggplot will not add a legend to my graph. I looked through the other help pages on this site concerning the same issue, but nothing I tried worked. Maybe based on my data I need to find another way to arrange things, but again, nothing I have tried has worked out. Thank you for your help!
Welcome to the forum. You're experencing this problem because you have to two geom_line functions going. Typically ggplot will only produce it automatically if you have one set. In the condition of two, you can either keep both separate and create a manual legend or you can merge it together and get it to work. Have a look here: https://rpubs.com/euclid/343644