R Vectorisation

R Vectorisation

# vectorised function
vectorised <- function(x, y) 
  {
    r = exp(-abs(x-y))
    return(r)
  }
 
#devectorised function
devectorised <- function(x,y) 
{
  r=rep(NA, length(x))
  for(i in seq_along(x))
  {
    r[i]= exp(-abs(x[i]-y[i]))
  }
  return(r)
 
}
 
# data
x= 1:2e6
y= x * 2
 
# tldr RESULTS !!!!!!!!!!!!!!!!!!
library(microbenchmark) 

microbenchmark(
  vectorised(x,y),
  devectorised(x,y), 
  unit = "s", times=5)