library(openxlsx)

sample1<-read.xlsx("http://kanggc.iptime.org/book/data/gdp-a.xlsx")

y.ts<-ts(sample1$GDP, start=2000, end=2017, frequency=1)
y.ts

lagy<-lag(y.ts, k=-1)
lagy

gy<-(y.ts-lagy)/lagy*100
gy

ly.ts<-log(y.ts)
ly.ts

gly<-(ly.ts-lag(ly.ts, k=-1))*100
gly

agy<-mean(gy)
agy

gy.ts<-((y.ts[18]/y.ts[1])^(1/17)-1)*100
gy.ts

plot(gy, type="l", lwd=3, col="red", main="Exact Growth Rate vs. Approx. Growth Rate of GDP")
lines(gly, lwd=3, lty=6, col="green")