C <- ggplot(farnorth, aes(x = month, y = Temperature))+
geom_boxplot(data = farnorth, fill = "grey", alpha = 0.5)+
geom_line(data = mean_temp3, aes(y = plus_one_degree, group = 1), colour = "#D55E00")+
geom_line(data = mean_temp3, aes(y = plus_two_degrees, group = 1), colour = "darkblue")+
geom_line(data = mean_temp3, aes(y = plus_three_degrees, group = 1), colour= "#009E73")+
labs(x = "Months", y = "Sea temperature in °C")+
scale_y_continuous(limits = c(0,22),
breaks = seq(0,22,4))+
theme_light()
I want to add a legend for the the 3 geom_lines.
ex: First geom_line = "Mean +1"
Second geom_line = "Mean +2"
Third geom_line = "Mean +3"