draw multiple line a+b*x in ggplot code example

Example 1: ggplot2 multiple lines geom_line

ggplot(economics, aes(x=date)) + 
  geom_line(aes(y = psavert), color = "darkred") + 
  geom_line(aes(y = uempmed), color="steelblue", linetype="twodash")

Example 2: ggplot2 multiple lines geom_line

# Visualization
ggplot(df, aes(x = date, y = value)) + 
  geom_line(aes(color = variable, linetype = variable)) + 
  scale_color_manual(values = c("darkred", "steelblue"))