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# reversing output of numpy argsort

Posted on 2013-06-20
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Hi,

I find it amazing that I can't find an answer online, but how do I use numpy argsort to sort in reverse order?  The documentation is sparse.

I'm sorting a simple array of numbers and need the sorted index values in descending order.

ideas?

Thanks!
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Question by:ugeb
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LVL 23

Expert Comment

ID: 39264084
I don't know a lot about Python, but ran across this, so i thought i'd toss it at you,

L2.reverse()

I grabbed this from page 17,
http://koen.me/research/teaching-asci/python-workshop-slides.pdf
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LVL 11

Author Comment

ID: 39264119
Thanks, but that has nothing to do with numpy's argsort.  That's plain python but I'm using numpy's data structure.
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LVL 23

Expert Comment

ID: 39264154
I apologise if i'm barking up the wrong tree, just trying to help,

Take a look here,
http://stackoverflow.com/questions/8445323/reverse-sort-and-argsort-in-python

This seems to be a solution.
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LVL 11

Author Comment

ID: 39264167
Thanks, but I've been through all these pages already through extensive searching, and they don't address the actual issue. None of the pages I've found have answered my question.
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LVL 23

Expert Comment

ID: 39264197
I wish i could help further but i can't. Hopefully another more qualified expert will help out.

Good luck.
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LVL 11

Accepted Solution

ugeb earned 0 total points
ID: 39264280
Thanks anyway.  I'm having to take the longer path of converting to a list and then reversing, instead of the far more efficient path of argsort actually having a reverse argument!  Oh well.
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LVL 11

Author Closing Comment

ID: 39274201
Thanks anyway.  I'm having to take the longer path of converting to a list and then reversing, instead of the far more efficient path of argsort actually having a reverse argument!  Oh well.
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