| Re: Huh?? Stddev went crazy! [message #59853] |
Wed, 16 April 2008 12:41  |
Conor
Messages: 138
Registered: February 2007
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Senior Member |
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On Apr 16, 3:31 pm, pgri...@gmail.com wrote:
> Conor wrote:
>> I'd like to see someone explain this one. My stddev function
>> apparently lost all grasp on reality?
>
>> IDL> print,stddev([1,2,3,4,5])
>> 3.07421 3.24566 3.08206 3.26360 2.97446
>> IDL> print,stddev([1.,2.,3.,4.,5.])
>> 3.07421 3.24566 3.08206 3.26360 2.97446
>> IDL> print,stddev([1.,2.])
>> 3.07421 3.24566
>
>> IDL> print,stddev(findgen(32))
>> 2.99513 3.07421 3.24566 3.08206 3.26360
>> 2.97446 2.96850 3.04474 2.66875 2.77181
>> 2.83465
>> 2.77395 2.77370 2.87829 2.84716 2.86982
>> 2.98503 2.93160 2.77602 2.59318 2.83169
>> 3.30869
>> 2.67353 3.15337 3.19076 3.19499 2.96050
>> 3.13871 2.61707 2.77854 3.12603 3.20029
>
>> Finally I did this:
>
>> IDL> .reset
>
>> And it returned to normal! Yeah!
>
>> IDL> print,stddev(findgen(32))
>> % Compiled module: STDDEV.
>> % Compiled module: MOMENT.
>> 9.38083
>> IDL> res = findgen(10,10)
>> IDL> print,stddev(res)
>> 29.0115
>
>> I have not been able to reproduce the crazy behavior since (not that
>> I've tried very hard). Still, it's rather worrisome if the behavior
>> of a built in function isn't reliable!!
>
> Well, here I think I should point out that "stddev" is not a "built-
> in"
> function, but a "library" function (meaning it is distributed as
> a .pro file).
> Hence, anybody can override it by compiling a different function
> called stddev. On the other hand, built-in functions
> cannot be overridden in that way.
>
> Paolo
I think you guys have solved it! I guess that wasn't that hard... I
don't know for sure but it is very likely that I had an array named
stddev. I had never realized that could create a potential conflict!
I went ahead and put compile_opt IDL2 in my startup file, so hopefully
I won't have to worry about this anymore! Now I know what to look for
though...
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