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Re: Inconsistent Mean Calculation [message #30836 is a reply to message #30828]

Mon, 20 May 2002 18:00

Mark Hadfield
Messages: 783
Registered: May 1995

Senior Member

"Phil" <plmcelwee@yahoo.com> wrote in message
news:a3589d11.0205201557.1a92499f@posting.google.com...
> I have 5000 frames of video in a NetCDF file, and I want to
> calculate the average of frame 2557. I have read the video file
> into both IDL v5.1 and Matlab v6.1. Additionally I have extracted
> frame 2557 and copied it into Excel. Here are the mean calculations
> I get for this frame:
>
> Matlab: 4092.6805
> Excel: 4092.6805
> IDL: 4093.6165
>
> Can anyone offer any suggestions as to why the IDL calculation is
> different?

Matlab uses double-precision real numbers whereas IDL by default uses
single-precision. Try repeating your IDL calculations using
double precision (for example, if you are using IDL's TOTAL function,
set its DOUBLE keyword).

--
Mark Hadfield "Ka puwaha et tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)

>

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[Message index]

		Re: Inconsistent Mean Calculation By: plmcelwee on Tue, 21 May 2002 10:39
		Re: Inconsistent Mean Calculation By: Mark Hadfield on Mon, 20 May 2002 18:00
		Re: Inconsistent Mean Calculation By: Kenneth P. Bowman on Mon, 20 May 2002 18:59

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