Avoid two for loops in R

Question

I have a R code that can do convolution of two functions...

convolveSlow <- function(x, y) {  
nx <- length(x); ny <- length(y)  
xy <- numeric(nx          


        

Answer 1

How about convolve(x, rev(y), type = "open") in stats?

> x <- runif(1000)
> y <- runif(1000)
> system.time(a <- convolve(x, rev(y), type = "o"))
   user  system elapsed 
  0.032   0.000   0.032 
> system.time(b <- convolveSlow(x, y))
   user  system elapsed 
 11.417   0.060  11.443 
> identical(a,b)
[1] FALSE
> all.equal(a,b)
[1] TRUE