2개의 y축 그래프 그리기

latticeExtra 패키지의 doubleYScale() 함수를 이용

#install.packages("latticeExtra")
require(latticeExtra)
data <- ggplot2::economics
str(data)
## Classes 'tbl_df', 'tbl' and 'data.frame':    574 obs. of  6 variables:
##  $ date    : Date, format: "1967-07-01" "1967-08-01" ...
##  $ pce     : num  507 510 516 513 518 ...
##  $ pop     : int  198712 198911 199113 199311 199498 199657 199808 199920 200056 200208 ...
##  $ psavert : num  12.5 12.5 11.7 12.5 12.5 12.1 11.7 12.2 11.6 12.2 ...
##  $ uempmed : num  4.5 4.7 4.6 4.9 4.7 4.8 5.1 4.5 4.1 4.6 ...
##  $ unemploy: int  2944 2945 2958 3143 3066 3018 2878 3001 2877 2709 ...

step 1.

xyplot(pop + unemploy ~ date, data, type = "l")

step 2.

obj1 <- xyplot(pop ~ date, data, type = "l", lwd=2)
obj2 <- xyplot(unemploy ~ date, data, type = "l", lwd=2)
doubleYScale(obj1, obj2, add.ylab2 = TRUE)

Step 3. 범례 추가

doubleYScale(obj1, obj2, text = c("population", "unemployment") , add.ylab2 = TRUE)