[R] what is wrong with my quicksort?

[warc]

the error message I get is:

           Error in while (x[j] >= pivot) { : Argument has length 0

so either pivot or x[j] is NULL.
 and it somestimes happens the first time the program enters the recursion,
sometimes the 6. or anywhere inbetween.



jholtman wrote:
> 
> have you tried to debug it yourself.  All you said is that 'it went
> wrong'.  that is not a very clear statement of the problem.  If I were to
> start looking at it, I would put some print statements in it to see what
> is happening on eachpath and with each set of data.  Have you tried this?
> 
> Sent from my iPad
> 
> On Sep 3, 2011, at 21:51, warc <conny-clauss at gmx.de> wrote:
> 
>> Hey guys,
>> I tried to program quicksort like this but somethings wrong.
>> 
>> please help
>> 
>> 
>>    
>>> partition <- function(x, links, rechts){
>>>    
>>>    i <- links
>>>    j <- rechts
>>>    t <- 0                        
>>>    pivot <- sample(x[i:j],1)
>>>    
>>>    while(i <= j){
>>>        
>>>        while(x[i] <= pivot){    
>>>            i = i+1}
>>>            
>>>        while(x[j] >= pivot){    
>>>            j = j-1}
>>>            
>>>        if( i <= j){            
>>>            
>>>            t = x[i]
>>>            x[i] = x[j]
>>>            x[j] = t
>>>            
>>>            i=i+1
>>>            j=j-1
>>>            
>>>            }
>>>            print(pivot)    
>>>        
>>>        
>>>        }
>>>    #Rekursion
>>>    
>>>    if(links < j){                
>>>        partition(x, links, j)}            
>>>    if(i < rechts){                
>>>        partition(x, i, rechts)}
>>>    
>>>    return(x)
>>>    }
>>>    
>>> 
>>> quicksort <- function(x){
>>>        
>>> 
>>>        
>>>        partition(x, 1, length(x))
>>> }
>> 
>> 
>> 
>> thx
>> 
>> --
>> View this message in context:
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>> Sent from the R help mailing list archive at Nabble.com.
>> 
>> ______________________________________________
>> R-help at r-project.org 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.
> 
> ______________________________________________
> R-help at r-project.org 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.
> 


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