R语言：Sys.sleep()与Sys.time()

#睡眠2秒
Sys.sleep(2)

> Sys.time()
[1] "2016-12-14 23:52:10 CST"

testit <- function(x)
{
    p1 <- proc.time()
    Sys.sleep(x)
    proc.time() - p1 # The cpu usage should be negligible
}

> testit(3.7)
用户 系统 流逝 
0.00 0.00 3.71 

plot(0:10,0:10, type="n")

# let use the 'for' to put texts on graph:
for(i in 1:10)
    text(i,i, paste("**", i))

## let retard steps 1 sec
plot(0:10,0:10, type="n")
for(i in 1:9){
    text(i,i, paste("step", i))
    Sys.sleep(1) 
}