[R-gui] rank function problem

[Ulrike Grömping]

Ibtesam,

you are using the wrong mailing list, you should be using R-help, not 
the GUI list.

Anyway, if you execute "print(z,digits=20)", you see that the reason for 
your different ranks is in numerical accuracy of representations of the 
numbers.

Regards,
Ulrike

ibtesam al_sagaf schrieb:
> Dear all
>
>  
>
> I'm Ibtesam. 
>
> I use R program in my studded.
> I have been seeing  problem in rank function. It works as a wrong way from vector to other.
>  
> I run this code many times, in every time I obtained this result;
>  
> 1-     When I enter this data vector manually, I obtain the correct ranking. It gives the same rank for equal values.  
> Example from the following data: rank(abs(0.2,0.2,-0.2))= 4  4 4
>  
>   
>> k=c(-.9,.2,-1.1,.5,-.8,.3,-1,.6,-1.3,-.2,-1.5,.1,-1.2,-.1,-1.4,.2,-.6,.5,-.8,.8)
>> rank(abs(k))
>>     
>  [1] 14.0  4.0 16.0  7.5 12.0  6.0 15.0  9.5 18.0  4.0 20.0  1.5 17.0  1.5 19.0
> [16]  4.0  9.5  7.5 12.0 12.0
> 2-     When I obtain the same data vector from some operations, I obtain a wrong ranking. It gives the different ranks for equal values.  
> Example from the following data: rank(abs(0.2,-0.2,0.2))= 3  4.5  4.5
>  
>
>
>   
>> x=c(2.9,3,2.5,2.6,3.2)
>> y=c(3.8,2.7,4,2.4)
>> z=rep(0,length(x)*length(y))
>>       sizez=1
>>       for(i in 1:length(x))
>>     
> +          for(j in 1:length(y))
> +      {z[sizez]=x[i]-y[j];  sizez=sizez+1;}
>   
>> z
>>     
>  [1] -0.9  0.2 -1.1  0.5 -0.8  0.3 -1.0  0.6 -1.3 -0.2 -1.5  0.1 -1.2 -0.1 -1.4
> [16]  0.2 -0.6  0.5 -0.8  0.8
>   
>>  R=rank(abs(z)) 
>> R
>>     
>  [1] 14.0  3.0 16.0  7.5 11.5  6.0 15.0 10.0 18.0  4.5 20.0  1.5 17.0  1.5 19.0
> [16]  4.5  9.0  7.5 11.5 13.0
>
>  
>
>  
>
> I try many times but I have not known what is the mistake.
> Can you kindly help me to solve this problem?
>  
> Thank you.
> Ibtesam.
>
>
>
>  
>
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