[r] How to make execution pause, sleep, wait for X seconds in R?

How do you pause an R script for a specified number of seconds or miliseconds? In many languages, there is a sleep function, but ?sleep references a data set. And ?pause and ?wait don't exist.

The intended purpose is for self-timed animations. The desired solution works without asking for user input.

Sys.sleep() will not work if the CPU usage is very high; as in other critical high priority processes are running (in parallel).

This code worked for me. Here I am printing 1 to 1000 at a 2.5 second interval.

for (i in 1:1000)
{
  print(i)
  date_time<-Sys.time()
  while((as.numeric(Sys.time()) - as.numeric(date_time))<2.5){} #dummy while loop
}