comp.lang.idl-pvwave archive: archive » Re: [Q]IDL: Using WHERE.

Home » Public Forums » archive » Re: [Q]IDL: Using WHERE.

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: [Q]IDL: Using WHERE. [message #5974 is a reply to message #5973]

Wed, 20 March 1996 00:00

rivers
Messages: 228
Registered: March 1991

Senior Member

In article <314F31C4.2C6B@cdc.noaa.gov>, Andy Loughe <afl@cdc.noaa.gov> writes:
> Joe Fitzgerald wrote:

>> Is there a way to use B to get the complementary values; i.e., the array
>> of subscripts for which ARRAY is less than 20?

> Uh! This is a set-up, isn't it?
> Is my boss watching?
> How about LESS THAN OR EQUAL TO? That would be complementary.
>
> Why use B? Why not use...
> C = Where(array LE 20., count)
> if (count gt 0) then print, 'Hurray!'

I think the idea was to use B to avoid the potentially expensive operation of
comparing the entire array again to find the complementary elements.

I think this will cut the computation time:

t = (array gt 20) ; t(i) will be 0 or 1 depending upon comparison
b = where(t) ; b is the indices of the > 20 elements
c = where(t-1) ; c is the indices of the <= 20 elements

This method avoids doing the floating point comparison twice.

____________________________________________________________
Mark Rivers (312) 702-2279 (office)
CARS (312) 702-9951 (secretary)
Univ. of Chicago (312) 702-5454 (FAX)
5640 S. Ellis Ave. (708) 922-0499 (home)
Chicago, IL 60637 rivers@cars3.uchicago.edu (Internet)

Report message to a moderator

[Message index]

		Re: [Q]IDL: Using WHERE. By: steinhh on Fri, 22 March 1996 00:00
		Re: [Q]IDL: Using WHERE. By: Paul Schopf on Thu, 21 March 1996 00:00
		Re: [Q]IDL: Using WHERE. By: Thomas A. McGlynn on Thu, 21 March 1996 00:00
		Re: [Q]IDL: Using WHERE. By: Mirko Vukovic on Wed, 20 March 1996 00:00
		Re: [Q]IDL: Using WHERE. By: rivers on Wed, 20 March 1996 00:00
		Re: [Q]IDL: Using WHERE. By: Andy Loughe on Tue, 19 March 1996 00:00

Previous Topic:	Re: Line index
Next Topic:	[Q]: How to calculate distance from GPS measurements

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 10 20:27:41 PDT 2025

Total time taken to generate the page: 0.08185 seconds