[R] detecting if a variable has changed

[S Ellison]

> > Nope, Ted. I asked for  a O(log(n)) solution, not an O(n) one.
> 
> I don't think that's possible with a numeric vector.  Inserting an entry
> at a random location is an O(n) operation, since you need to move all
> following values out of the way.

If the vector is presorted, wouldn't a binary search find the correct location in O(log(n))? (roughly log2(n)?) 

After that any insertion depends on how fast R can move memory about so the overall speed clearly depends on factors other than finding the location. 

S Ellison

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