| Re: Search routines [message #13006 is a reply to message #12851] |
Sat, 26 September 1998 00:00   |
R. Bauer
Messages: 137
Registered: November 1996
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Senior Member |
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Kenneth P. Bowman wrote:
> In article <3602D89B.15BF8C2D@ssec.wisc.edu>, Liam Gumley
> <Liam.Gumley@ssec.wisc.edu> wrote:
>
>> Kenneth P. Bowman wrote:
>>> IDL has a pretty good SORT routine, but no SEARCH routine that I have been
>>> able to find (that is, a procedure to find the index of the closest/first
>>> match in an ordered list). Once again, this can be done with loops, but
>>> such an implementation would almost certainly be much slower than a
>>> built-in function. Since searching and sorting are such basic operations,
>>> does anyone know why there is no SEARCH in IDL?
>>
>> How about the MIN function, e.g.
>>
>> array = findgen(100)
>> value = 37.2
>> result = min( abs( value - array ), location )
>> help, location
>
> Again, I'm sure this is an order-N operation, as MIN has to check every
> element, just like WHERE. It has no knowledge that the list is ordered.
>
> Ken
>
Hi Ken,
look at this routine.
The name should mean find_middling_indices. It was written in the past where we
have not the possibilty to use long names.
The help part could be added if you are interested.
In addition to a normal search this routine is able to use a window which is
usefull for some algorithm we have written.
We are thinking that's this routine is very fast, but any ideas to get it faster
are welcome.
Reimar
--
R.Bauer
Institut fuer Stratosphaerische Chemie (ICG-1)
Forschungszentrum Juelich
email: R.Bauer@fz-juelich.de
;
; Copyright (c) 1996, Forschungszentrum Juelich GmbH ICG-1
; All rights reserved.
; Unauthorized reproduction prohibited.
; This software may be used, copied, or redistributed as long as it is not
; sold and this copyright notice is reproduced on each copy made. This
; routine is provided as is without any express or implied warranties
; whatsoever.
;+
; NAME:
; fi_mi_in
;
; PURPOSE:
; The result of this function is a two dimensional indexfield.
; It is used to find the indices which overlaps in client time depending on
master time and time_window
; The first index is the start and the second the end index of the overlapping
values from client_time.
;
; CATEGORY:
; MATH
;
; CALLING SEQUENCE:
; Result=fi_mi_in(client,master,master_time_window,[/help])
;
; INPUTS:
; client: The client time
; master: The master time
; master_time_window: The time_window must have same size as master
;
; KEYWORD PARAMETERS:
; help: gives a short description
;
; OUTPUTS:
; This function returns a two dimensional indexfield
; The first index is the start and the second the end index of the used time
window
; -1 at an index means there were no results
;
; EXAMPLE:
; client=[1,2,3,4,5]
; master=[2,4]
; time_window=[0,0]
; Result=fi_mi_in(client,master,time_window)
; help,result
; RESULT LONG = Array[2, 2]
; print,result
; 1 1
; 3 3
;
;
; MODIFICATION HISTORY:
; Written by: R.Bauer (ICG-1), 1996-May-06
; 1998-Mar-02 much more efficiency by combining with suche.pro (F.Rohrer)
;
;-
FUNCTION fi_mi_in,client,master,time_window,help=help
if keyword_set(help) then begin
help,call=call
help_of_interest=within_brackets(call[0],brackets=['<','('])
message,help_calling_sequence(help_of_interest),/cont
return,-1
endif
laenge_master=(size(master))(1)
lstx=(size(client))(1)-1
remember=0
index=MAKE_ARRAY(2,laenge_master,type=3,value=-1)
FOR i=0L, laenge_master-1 DO BEGIN
k = LONG(remember)
WHILE client(k) LT master(i) -time_window(i) AND k LT lstx DO k=k+1
IF client(k) GE master(i) -time_window(i) and client(k) LE
master(i)+time_window(i) THEN BEGIN
index(0,i)=LONG(k)
remember=(index(0,i))(0)
ENDIF
if index(0,i) ne -1 then begin
mx = remember
WHILE client(mx) LE master(i)+time_window(i) and mx LT lstx DO mx=mx+1
if client(mx) LE master(i)+time_window(i) then index(1,i)=LONG(mx) else
index(1,i)=LONG(mx)-1
endif
ENDFOR
RETURN,index
END
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