[Tutor] Fwd: How to roughly associate the values of two numpy arrays, or python lists if necessary

[Peter Otten]

Shall, Sydney via Tutor wrote:

> What I want is the following.
> 
> I have:
> > property_a = [1, 6, 2, 4]
> > property_b = [62, 73, 31 102]
> 
> Result should approximately be:
> > property_b = [31, 102, 62, 73]
> 
> That is both lists change in value in exactly the same order.
> 
> Now, this is easy to achieve. I could simply sort both lists is
> ascending order and I would then have an exact alignment of values is
> ascending order. The correlation would be a perfect linear relationship,
> I suppose.
> 
> But my actual scientific problem requires that the correlation should be
> only approximate and I do not know how close to to a perfect correlation
> it should be. So, I need to introduce some lack of good correlation when
> I set up the correlation. How to do that is my problem.
> 
> I hope this helps to clarify what my problem is.

Maybe you could sort the already-sorted property_b again, with some random 
offset:

>>> import itertools
>>> def wiggled(items, sigma):
...     counter = itertools.count()
...     def key(item): return random.gauss(next(counter), sigma)
...     return sorted(items, key=key)
... 
>>> wiggled(range(20), 3)
[0, 5, 2, 4, 1, 6, 7, 8, 3, 9, 11, 10, 13, 14, 16, 12, 18, 17, 19, 15]
>>> wiggled([31, 102, 62, 73], .8)
[102, 31, 62, 73]
>>> wiggled([31, 102, 62, 73], .8)
[31, 102, 62, 73]
>>> wiggled([31, 102, 62, 73], .8)
[31, 102, 62, 73]
>>> wiggled([31, 102, 62, 73], .8)
[31, 62, 102, 73]