| Re: POLY_FIT 5.0: inaccurate results. use 4.0 if possible. [message #11527 is a reply to message #11308] |
Mon, 30 March 1998 00:00  |
pit
Messages: 92
Registered: January 1996
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In article <MPG.f859b08896d2aad989765@news.frii.com>,
davidf@dfanning.com (David Fanning) writes:
> I submitted this problem to the RSI technical support staff
> to see what they knew about it. Here is their response.
> This is one of those "nice things to do" that cause confusion
> because the change is not communicated carefully enough. I'm
> not sure how to solve this "upgrade" problem, but I do know
> it causes grief from time to time.
>
> ************
> To obtain similar results for the POLY_FIT procedure from IDL 4.0.1 to
> IDL 5.0, please set (/DOUBLE) the DOUBLE keyword when using POLY_FIT in
> IDL 5.0.� For most of IDL 4.0.1 numerical analysis routines, the
> internal computations are performed on double precision variables.
> However, because of timing feature requests, these routines were changed
> to perform single precision computations.� Fortunately, the DOUBLE
> keyword was added to these routines to force double precision
> computations.� Thus, to force IDL 5.0's POLY_FIT to perform like IDL
> 4.0.1's POLY_FIT, please use this DOUBLE keyword.� Sorry for any
> inconvenience this change may have caused.
> *************
So, why don't they use a keyword /SINGLE and stay backward compatible?
This is bad style, IHMO.
Peter
--
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Peter "Pit" Suetterlin http://www.uni-sw.gwdg.de/~pit
Universitaets-Sternwarte Goettingen
Tel.: +49 551 39-5048 pit@uni-sw.gwdg.de
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