college acceptance & birth

dta<- read.table("birth_college.txt", h=T)
##嘗試一只有一軸
library(ggplot2)
ggplot(dta, aes(Year,Birth))+
 geom_line() + 
 geom_point() +
 theme_minimal()

##嘗試二加入兩個geom_line，是成功的
ggplot() +
 geom_line(data=dta, aes(Year,Birth)) +
 geom_line(data=dta, aes(Year,Entrance),
           linetype="dotted") +
 geom_point(data=dta, 
            aes(Year, Birth),
            pch=16) +
 geom_point(data=dta, 
            aes(Year, Entrance),
            pch=1) +
 labs(x="Year",
      y="Birth") +
theme_minimal()