| Re: findgen anomaly? [message #67315 is a reply to message #67314] |
Fri, 10 July 2009 14:52  |
David Fanning
Messages: 11724
Registered: August 2001
|
Senior Member |
|
|
Chris Chronopoulos writes:
> this morning i decided to write up a short function that would return
> a list of values given a min, max and increment (like Mathematica's
> Range[] function) but it was giving me some problems. i narrowed it
> down to an oddity in findgen, which can described by the following
> example:
>
> IDL> min=5.5
> IDL> max=6.2
> IDL> increment=0.1
> IDL> print, (max-min)/increment+1
> 8.00000
> IDL> print,findgen(8.00000)
> 0.00000 1.00000 2.00000 3.00000 4.00000
> 5.00000
> 6.00000 7.00000
> IDL> print, findgen((max-min)/increment+1)
> 0.00000 1.00000 2.00000 3.00000 4.00000
> 5.00000
> 6.00000
>
> now, by any reasonable system of logic, shouldn't the last two lines
> produce the same result? the correct result, of course, is the first
> on that goes all the way up to 7.00000. the weird thing is that if you
> change max from 6.2 to 6.3, it works fine. it seems there are certain
> values that give it problems, while others work fine.
>
> what is going on here?
Golly, it has been several weeks since we had to pull
this article out:
http://www.dfanning.com/math_tips/sky_is_falling.html
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
