comp.lang.idl-pvwave archive: archive » Re: TOTAL gives totally different result on identical array

Home » Public Forums » archive » Re: TOTAL gives totally different result on identical array

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: TOTAL gives totally different result on identical array [message #76903 is a reply to message #76899]

Fri, 08 July 2011 03:34

Fabzou
Messages: 76
Registered: November 2010

Member

Funny, It looks like the post I wrote a couple of days ago. You should
have a look to this thread :

http://groups.google.com/group/comp.lang.idl-pvwave/browse_t hread/thread/47482e565173a127/b58f3a3ba7934b93?#b58f3a3ba793 4b93

On 07/08/2011 12:22 PM, M. Suklitsch wrote:
> Hi everybody,
>
>
> I don't exactly know how to start this question, so I'll probably just
> tell you the workflow which leads to a very disturbing result.
>
> I have a netCDF file which contains temperature data for a decade on
> daily time resolution. And I have two different versions of an IDL
> based evaluation tool which should read in the data and do some stuff
> with it.
>
> Now, although I read in exactly the same data (the data array has the
> same size in both IDL sessions with both versions of my tool), TOTAL
> and MEAN give completely different results. And I do not understand
> how that can be, since the data does not contain any NaN values, and
> MIN and MAX of the array are identical in both IDL sessions. The only
> difference between the two IDL sessions are different source codes
> that lead to the point where I do the stuff below. Here is what I get:
>
> Session 1:
> =======
> IDL> ncid=NCDF_OPEN('my_input_file.nc')
> IDL> ncdf_varget, ncid, 'tas', testa
> IDL> help, mean(testa), min(testa), max(testa)
> <Expression> FLOAT = 270.284
> <Expression> FLOAT = 232.614
> <Expression> FLOAT = 317.723
> IDL> print, total(testa)/n_elements(testa)
> 270.284
> IDL> print, n_elements(testa)
> 127124400
> IDL> print, total(testa)
> 3.43597e+10
> IDL> idx=where(testa lt 275., countidx, ncomplement=countnidx)
> IDL> help, countidx, countnidx
> COUNTIDX LONG = 22074445
> COUNTNIDX LONG = 105049955
>
>
> Session 2:
> =======
> IDL> ncid=NCDF_OPEN('my_input_file.nc')
> IDL> ncdf_varget, ncid, 'tas', testa
> IDL> help, mean(testa), min(testa), max(testa)
> <Expression> FLOAT = 67.5711
> <Expression> FLOAT = 232.614
> <Expression> FLOAT = 317.723
> IDL> print, total(testa)/n_elements(testa)
> 67.5711
> IDL> print, n_elements(testa)
> 127124400
> IDL> print, total(testa)
> 8.58993e+09
> IDL> idx=where(testa lt 275., countidx, ncomplement=countnidx)
> IDL> help, countidx, countnidx
> COUNTIDX LONG = 22074445
> COUNTNIDX LONG = 105049955
>
>
> So, the values within the arrays seem to be the same (since the
> counting gives the identical number of elements), yet the TOTAL (and
> MEAN) deviate completely from each other. How can that be? I am really
> confused right now. And insecure about any results I got so far.
>
>
> Regards,
> Martin

Report message to a moderator

[Message index]

		Re: TOTAL gives totally different result on identical array By: Michael Galloy on Fri, 08 July 2011 12:10
		Re: TOTAL gives totally different result on identical array By: Liam Gumley on Fri, 08 July 2011 11:48
		Re: TOTAL gives totally different result on identical array By: Foldy Lajos on Fri, 08 July 2011 11:33
		Re: TOTAL gives totally different result on identical array By: Fabzou on Fri, 08 July 2011 10:46
		Re: TOTAL gives totally different result on identical array By: Liam Gumley on Fri, 08 July 2011 10:25
		Re: TOTAL gives totally different result on identical array By: Foldy Lajos on Fri, 08 July 2011 08:44
		Re: TOTAL gives totally different result on identical array By: Liam Gumley on Fri, 08 July 2011 07:37
		Aw: Re: TOTAL gives totally different result on identical array By: M. Suklitsch on Fri, 08 July 2011 05:55
		Re: TOTAL gives totally different result on identical array By: Fabzou on Fri, 08 July 2011 03:34

Previous Topic:	Variable is undefined: Actually a function
Next Topic:	Weighted correlation

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sun Oct 12 04:38:17 PDT 2025

Total time taken to generate the page: 1.84232 seconds