R ggplot vary line thickness or style based on conditional

Question

Here is a link to a .csv of my data, which I call "pop_c".

I generate a line plot using the following code:

ggplot(data = pop_c, aes(x = year, y = pop_change, color = state)) + 
  geom_line(stat="identity")

但是，我想根据“衰退”列改变线条的粗细、样式或阴影。如果“衰退”列中的值为 1，我希望该线为：a) 更粗，b) 阴影更深，或 c) 两者的某种组合。

有人可以解释如何根据这样的条件改变线条的粗细、样式和/或阴影吗？

Answer 1

添加alpha=recession或size=recession或linetype=recession成aes()