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Re: sorting string arrays - non alphabetic and user defined order [message #50910 is a reply to message #50820]

Mon, 23 October 2006 14:03

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Tue, 17 Oct 2006 06:00:03 -0600, David Fanning wrote:

> Greg Michael writes:
>
>> hmm... it seems to me that 'result' is the array you are looking for:
>> it has the elements in the order you want, and they have the indices
>> numbered from zero (i.e. there are no empty elements).
>
> It seems that way to me, too. But I had to work with
> the solution for a time before I understood it. It
> would have taken me a LONG time to think of using
> indices rather than strings to come up with a solution.
> Perhaps the solution was TOO concise. I've expanded on
> it just a little bit in this article:
>
> http://www.dfanning.com/idl_way/strsort.html

This is similar to the standard inflate and compare WHERE_ARRAY
method. So it would be somewhat simpler (if a bit slower) just to
say:

mylist=mylist[sort(where_array(mylist,namelist,/PRESERVE_ORD ER))]

see turtle.as.arizona.edu/idl/where_array.pro for the modified version
which includes PRESERVE_ORDER.

That said, this exhibits the classic defect of
"scale-em-up-and-compare" methods which the REBIN/REFORM stuff
enables: it starts to get ugly when your comparison vectors get long,
scaling as the product of their lengths, and gobbling up enormous
amounts of memory in the process. We discuss in detail the pros and
cons of the various methods here:

http://www.dfanning.com/tips/set_operations.html

For long vectors, you'll be better off with a sort-based algorithm
(e.g. ind_int_SORT, see above):

mylist=mylist[sort(ind_int_sort(namelist,mylist))]

JD

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[Message index]

		sorting string arrays - non alphabetic and user defined order By: rkombiyil on Mon, 16 October 2006 03:34
		Re: sorting string arrays - non alphabetic and user defined order By: David Fanning on Tue, 17 October 2006 05:00
		Re: sorting string arrays - non alphabetic and user defined order By: JD Smith on Mon, 23 October 2006 14:03
		Re: sorting string arrays - non alphabetic and user defined order By: greg michael on Tue, 17 October 2006 04:43
		Re: sorting string arrays - non alphabetic and user defined order By: rkombiyil on Sun, 22 October 2006 17:53
		Re: sorting string arrays - non alphabetic and user defined order By: rkombiyil on Tue, 17 October 2006 00:56
		Re: sorting string arrays - non alphabetic and user defined order By: greg michael on Tue, 17 October 2006 00:14
		Re: sorting string arrays - non alphabetic and user defined order By: greg michael on Tue, 24 October 2006 00:39

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