R help - May 2007 - help with executing instruction every i-th run of loop

if (i %% 1000 == 0)

b

On May 17, 2007, at 10:56 AM, Mark W Kimpel wrote:
> I am running a very long loop and would like to save intermediate
> results in case of a system or program crash. Here is the skeleton of
> what my code would be:
>
> for (i in 1:zillion)
>    {
>     results[[i]]<-do.something.function()
>     if (logical.test(i)) {save(results, "results.tmp")}
>    }
>
> logical.test would test to see if i/1000 has no remainder. What R
> function would test that?
>
> Is there an even better way to address my need?
>
> Thanks,
> Mark
> --  
>
> ---
>
> Mark W. Kimpel MD  ** Neuroinformatics ** Dept. of Psychiatry
> Indiana University School of Medicine
>
> 15032 Hunter Court, Westfield, IN  46074
>
> (317) 490-5129 Work, & Mobile & VoiceMail
> (317) 663-0513 Home (no voice mail please)
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting- 
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> and provide commented, minimal, self-contained, reproducible code.


--
Benilton Carvalho
PhD Candidate
Department of Biostatistics
Bloomberg School of Public Health
Johns Hopkins University
bcarvalh at jhsph.edu

I am running a very long loop and would like to save intermediate 
results in case of a system or program crash. Here is the skeleton of 
what my code would be:

for (i in 1:zillion)
   {
    results[[i]]<-do.something.function()
    if (logical.test(i)) {save(results, "results.tmp")}
   }

logical.test would test to see if i/1000 has no remainder. What R 
function would test that?

Is there an even better way to address my need?

Thanks,
Mark
-- 

---

Mark W. Kimpel MD  ** Neuroinformatics ** Dept. of Psychiatry
Indiana University School of Medicine

15032 Hunter Court, Westfield, IN  46074

(317) 490-5129 Work, & Mobile & VoiceMail
(317) 663-0513 Home (no voice mail please)

Mark W Kimpel wrote:
> I am running a very long loop and would like to save intermediate 
> results in case of a system or program crash. Here is the skeleton of 
> what my code would be:
> 
> for (i in 1:zillion)
>    {
>     results[[i]]<-do.something.function()
>     if (logical.test(i)) {save(results, "results.tmp")}
>    }
> 
> logical.test would test to see if i/1000 has no remainder. What R 
> function would test that?

    !(i %% 1000)

Uwe Ligges

> Is there an even better way to address my need?
> 
> Thanks,
> Mark

On 5/17/2007 10:56 AM, Mark W Kimpel wrote:
> I am running a very long loop and would like to save intermediate 
> results in case of a system or program crash. Here is the skeleton of 
> what my code would be:
> 
> for (i in 1:zillion)
>    {
>     results[[i]]<-do.something.function()
>     if (logical.test(i)) {save(results, "results.tmp")}
>    }
> 
> logical.test would test to see if i/1000 has no remainder. What R 
> function would test that?
(i %% 1000) == 0

Duncan Murdoch

Mark W Kimpel wrote:
> I am running a very long loop and would like to save intermediate 
> results in case of a system or program crash. Here is the skeleton of 
> what my code would be:
> 
> for (i in 1:zillion)
I'm a bit worried about this line:

  > 1:zillion
  > Error: cannot allocate vector of size 4 zillion bytes

  hmm, lets try on a machine with a few more zillion bytes of RAM:

  > 1:zillion
  Error: result would be too long a vector
> Is there an even better way to address my need?
  Looping over vectors like this involves the uneccesary creation of a 
long vector. For anything up to a million its probably okay, but once 
you start getting into the zillions...

  You can do it with less storage by just having a while loop:

  > while (i != 100 ){print(i);i=i+1}

  Many modern computer languages have "iterators" for looping, which 
abstract all the looping functionality into an object. I started writing 
something for R a few years ago but never got round to finishing it. It 
let you do this:

  myLoop <- loop(N=10,step=1,start=1)
  while(iterate(myLoop)){
   doSomething()
  }

  The 'myLoop' object here is the iterator that controls the looping. 
You can use it to get the iteration number and then use the  i %% 1000 
test everyone else has told you about by now...

  Anyway, if anyone has a spare R programmer kicking around and would 
like all my looper code, just ask...

Barry