| Re: N_ELEMENTS and WHERE: Scalar or Array ? [message #14205 is a reply to message #14130] |
Mon, 01 February 1999 00:00   |
Craig Markwardt
Messages: 1869
Registered: November 1996
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Senior Member |
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wmc@bas.ac.uk writes:
> ...
> But since this has come up, & its one of my pet peeves: why cannot where
> return a null array to indicate no-elements-match. And then array[null] would
> match to nothing. This would allow one to say
>
> array[where(wurble)]='stoat'
>
> instead of the ugly
>
> i=where(wurble,count)
> if (count gt 0) then array[i]='stoat'
>
Amen brother! It is sadly unfortunate that where(0) returns a number
at all. A null array -- if IDL had them! -- would be the best.
Of course, there is the trade-off between power user and newbie user.
Consider the following:
wh_one = where(x GT 1)
x[wh_ine] = 0 ; NOTE the type
Because of the typo, the second statement would have the mysterious
side effect of having no effect at all! (including no error message) I
would still love to have it, but newbies might go crazy.
Craig
--
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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@astrog.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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