How to sort unsort: array(1).sort transform of array(2) -> array(3).unsort (reversed array(1).sort

Question

How do you sort, operate on, and then unsort the result?

Assume I have a float array p1 = 0.15,0.3, 0.25, 0.12, .... It is sorted to: p2 = sort(p1

Answer 1

You need a double argsort here to keep the order:

In [6]: a
Out[6]: array([5, 4, 8, 3, 6, 1, 2, 4, 9, 6])

In [7]: b=sort(a)

In [8]: b
Out[8]: array([1, 2, 3, 4, 4, 5, 6, 6, 8, 9])

In [9]: ii=a.argsort().argsort()

In [10]: c=b*b

In [11]: c
Out[11]: array([ 1,  4,  9, 16, 16, 25, 36, 36, 64, 81])

In [12]: c[ii]
Out[12]: array([25, 16, 64,  9, 36,  1,  4, 16, 81, 36])