| Re: Sort without loops [message #45162 is a reply to message #45159] |
Wed, 17 August 2005 07:24   |
R.Bauer
Messages: 1424
Registered: November 1998
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Senior Member |
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Ian Dean wrote:
> Hi All,
> I have a large string array (~100000 elements) that need sorting on two
> fields within each string.
>
> e.g. array=['F;100', 'ABC;6', 'DE;2', 'DE;10', 'DE;1']
>
> Order required is a) sort items to left of ';' followed by b) sort items
> numerically to right of ';'
> This would produce:
> ABC;6 DE;1 DE;2 DE;10 F;100
>
> A simple sort (sort(array)) procudes:
> ABC;6 DE;1 DE;10 DE;2 F;100
>
> The only way I've found is to conmvert the RH part to I4.4 format within a
> loop and search on the new values:
> ......
> for j=0, n_elements(array)-1 do begin
> parts=strsplit(array[j], ';', /extract)
> RH=string(fix(parts[1]), format='(I4.4)')
> new[j]=parts[0]+RH
> endfor
> order=sort(new)
> ...
> i.e
> new array is F;0100 ABC;0006 DE;0002 DE;0010 DE;0001
> which is then sorted correctly.
>
> Is there a clever way of sorting on two fields like this without using a
> loop. The above algorithm is faaaar slower than just using sort.
>
> I hope I have made this as clear as mud.#
>
> In expectation,
> Ian
>
>
probably n_sort is what you want.
http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_source/idl _html/dbase/n_sort_dbase.pro.html
cheers
Reimar
--
Reimar Bauer
Institut fuer Stratosphaerische Chemie (ICG-I)
Forschungszentrum Juelich
email: R.Bauer@fz-juelich.de
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a IDL library at ForschungsZentrum Juelich
http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_lib_intro. html
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