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Re: Ordering function weird?


Claus wrote:
> Hi,
> say I've got two sets of number, x and y, which I want to rank. See the 
> example below. I totally expect and want the result of Ordering[x]. But 
> I neiter understand nor expect the result of Ordering[y]. Both Sort[x] 
> and Sort[y] are ok.
> Can anybody explain to me Ordering[y]?

What do you find "weird" about it?  It gives the result I expect: 
y[[Ordering[y]]] is the same as Sort[y].

> 
> 
> In[3]:= x = {1, 2, 3, 6, 10, 3, 4}
> y = {1, 2, 7, 8, 9, 1, 2}
> 
> Out[3]= {1, 2, 3, 6, 10, 3, 4}
> 
> Out[4]= {1, 2, 7, 8, 9, 1, 2}
> 
> In[5]:= Sort[x]
> Sort[y]
> 
> Out[5]= {1, 2, 3, 3, 4, 6, 10}
> 
> Out[6]= {1, 1, 2, 2, 7, 8, 9}
> 
> In[7]:= Ordering[x]
> Ordering[y]
> 
> Out[7]= {1, 2, 3, 6, 7, 4, 5}
> 
> Out[8]= {1, 6, 2, 7, 3, 4, 5}
> 


-- 
Szabolcs


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