[R] 'break' function in loop

[Rui Barradas]

Hello,


jholtman wrote
> 
> I have never seen 'break' used in an 'ifelse'; you probably meant to
> use an 'if' statement there.
> 
> On Thu, Mar 1, 2012 at 8:24 AM, Tsai, Pei-Chien
> <pei-chien.tsai at .ac> wrote:
>> Dear R helpers,
>>
>> I have some difficulties in using 'break' function with loop, and the
>> followings are my script. What I try to do is (1) permute 'or' first; (2)
>> doing t-test if this 'or' pass criteria 1 (k=1); (3) end the loop when I
>> get 10 permutations; (4) redo everything again but this time use criteria
>> 2 (k=2) (I have more criteria 1:n).
>>
>> Somehow using my script, the final dataset (results1) only contains the
>> result from criteria 1 (twice!) but not the result from criteria 2. I
>> guess probably I put the break function under the wrong loop but I cannot
>> fix it. Sorry if the whole script looks quite messy, I will be very
>> appreciate if someone can help me fix this problem or probably give me
>> some advices to write it in a smart way.
>>
>>
>> My attempt:
>>
>> controlall <- rbeta(10000,1.5,6)
>> caseall <- rbeta(10000,1.6,6)
>>
>> results <- NULL
>> results1 <- NULL
>> or <-vector("list",length=10)
>> criteria <- matrix(data=c(1.05,1.15,1.15,1.25),ncol=2,nrow=2)
>>
>> for (k in 1:2) {
>>
>> for (i in 1:1000)
>>     {
>>         control <- sample(controlall,100)
>>         case <- sample(caseall,100)
>>         or[i] <-
>> round(mean(case)*(1-mean(control))/(mean(control)*(1-mean(case))),digit=2)
>>
>>  if (or[i]<criteria[k,2]&or[i]>=criteria[k,1])
>>  {
>>     group <- c(rep(1,100),rep(0,100))
>>     value <- c(case,control)
>>     ttest <-
>> (t.test(case,control,alternative="two.sided",paired=F))$p.value
>>     all <- c(or[i],ttest)
>>     results <- rbind(results,all)
>>  }
>>         ifelse(nrow(results)==5,break,1)
>>  }
>>    results1 <- rbind(results1,results)
>>  }
>>
>>
>> Thank you so much in advance,
>> Amber
>>
>>        [[alternative HTML version deleted]]
>>
>> ______________________________________________
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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
> 
> 
> 
> -- 
> Jim Holtman
> Data Munger Guru
> 
> What is the problem that you are trying to solve?
> Tell me what you want to do, not how you want to do it.
> 
> ______________________________________________
> R-help@ mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 


Right.
There are other things I'd like to note:
1. When debugging, if you use random number generators, also use 'set.seed'.
And get reproducible
    conditions for the code tests.

2. Your first 'if' has the short conjunction '&'. This is a vectorized
version, you only want 1 result.
    See

    ?"&&".

    (Jim's statement is another 'vectorized' vs. '1 result' case. You want
the latter on both cases.)

3. Now the bug. You don't reinitialize 'results' to NULL and it therefore
reuses the first one.
    It's a good pratice to always put 'var <- NULL' as the instruction just
before the loop that forms it.

Is this what you want?


set.seed(1)   # Note 1 above
results1 <- NULL
for (k in 1:2) {
	results <- NULL   # Note 3 above.
	for (i in 1:1000)
	{
      	control <- sample(controlall, 100)
      	case <- sample(caseall, 100)
      	or[i] <-
round(mean(case)*(1-mean(control))/(mean(control)*(1-mean(case))), digit=2)

		if (or[i] < criteria[k,2] && or[i] >= criteria[k, 1])   # Note 2 above
		{
			group <- c(rep(1,100),rep(0,100))
			value <- c(case,control)
			ttest <- (t.test(case,control,alternative="two.sided",paired=F))$p.value
			all <- c(or[i], ttest)
			results <- rbind(results, all)
		}
		if(!is.null(results) && nrow(results) == 5) break      # Note 2 above
	}
	results1 <- rbind(results1, results)
}
results
results1


Hope this helps

Rui Barradas


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