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Re: N_ELEMENTS and WHERE: Scalar or Array ? [message #14221 is a reply to message #14130]

Fri, 29 January 1999 00:00

davidf
Messages: 2866
Registered: September 1996

Senior Member

Rose (rmlongfield@my-dejanews.com ) writes:

> Hi All, I keep making the same mistake with N_ELEMENTS so I decided
> to write and ask if anyone has found a solution. I use WHERE to find some
> zeroes in a data set which I want to exclude in further processing. Problem
> is that sometimes they are all zeroes. Using a simple :
>
> non_zero_xvalues = WHERE (subarray1 GT 0)
> IF(non_zero_array EQ -1) ...
>
> gets me into trouble because, when it is an array, I get an error. If I use
> N_ELEMENTS(non_zero_array) there is always at least one element, whether it
> is -1 or something else. I don't like ignoring the 'something else' value
> just because it is the only one. Is the answer another IF statement or some
> sort of error control?

The second positional parameter of the WHERE function is
an output variable that holds the "count" of the number
of elements found that meet the WHERE criteria. So the
proper sequence of commands looks something like this:

index = WHERE( array GT 0, count)
IF count GT 0 THEN ....

Cheers,

David

------------------------------------------------------
David Fanning
Fanning Software Consulting
Phone: 970-221-0438
E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		N_ELEMENTS and WHERE: Scalar or Array ? By: rmlongfield on Fri, 29 January 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: davidf on Wed, 03 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: steinhh on Wed, 03 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: wmc on Wed, 03 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: wmc on Wed, 03 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: Jack Saba on Tue, 02 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: steinhh on Tue, 02 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: Craig Markwardt on Mon, 01 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: wmc on Mon, 01 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: steinhh on Mon, 01 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: wmc on Mon, 01 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: Mark Buckley on Fri, 29 January 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: davidf on Fri, 29 January 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: David Ritscher on Fri, 29 January 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: David Kastrup on Fri, 29 January 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: R.Bauer on Fri, 29 January 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: David Ritscher on Thu, 04 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: Michael Werger on Thu, 04 February 1999 00:00
		Re: N_ELEMENTS and WHERE: Scalar or Array ? By: Annette Schloss on Wed, 03 February 1999 00:00

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