dependent nested for loops in R

On 1/30/21 8:26 PM, Shaami wrote:

Hi
I have very large dependent nested for loops that are quite expensive
computationally. It takes weeks and does not end to give me results.

Could

anyone please guide how could I use apply function or any other

suggestion

for such big and dependent loops in R? A sample code is as follows.

w = NULL
for(j in 1:1000)
{
   x = rnorm(2000)
   z = x[1]
   for(i in 2:2000)
   {
     z = x[i]+5*z[i-1]

I'm guessing you meant to type:

         z[i] <- x[i]+5*z[i-1]

     if(z>4 | z<1) {

And more guesses (in the absence of any sort of problem description)
that you really wanted:


  if(z[i]>4 | z[i]<1) {  ....

       w[j]=i
       break
     } else {
       w[j] = 0
     }
   }
}

Are you sure you need a for-loop? Seems like you could have done this
with a couple of vectorized operations. And the `break` looked entirely
superfluous.

Thank you

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