[R] Partial sort?

[Duncan Murdoch]

Duncan Murdoch wrote:
> rkevinburton at charter.net wrote:
>   
>> This is definitely a newbie question but from the documentation I have not been able to figure out what the partial sort option on the sort method does. I have read and re-read the documentation and looked at the examples but for some reason it doesn't register. Would someone attempt to explain what sort with a non-null partial array of indices does?
>>
>>   
>>     
> It guarantees that those particular indices are sorted correctly, but 
> doesn't guarantee anything else.  For example,
>
>  > x <- 10:1
>  > sort(x, partial=1)
>
> guarantees that the first entry in x (i.e. 10) is placed correctly, but 
> nothing else, and the result is:
>
>  [1]  1  9  8  7  6  5  4  3  2 10
>
>
>   
Oops, that's wrong.  It's entry 1 of the result which will be placed 
correctly.  This example shows the difference:

 > x <- rep(1:3, 4) + rep(1:4/10, each=3)
 > x
 [1] 1.1 2.1 3.1 1.2 2.2 3.2 1.3 2.3 3.3 1.4 2.4 3.4
 > sort(x, partial=2)
 [1] 1.1 1.2 1.3 1.4 2.2 3.2 3.1 2.3 3.3 2.1 2.4 3.4

Duncan Murdoch