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[ferret_users] Why does "regresst" show different result?



Dear Ferret users,

I did a simple experiment to see a linear trend of 1-D time series.
The data is attached here.
What I did is something like this:

'use ssh.nc'
'let p = t[gt=sla]'
'let q = sla'
'go regress'
'plot/vs p,what'

The result is good and it shows a reasonable graphic.
However, when I check the value of "slope", I think it is not correct.

'list slope'
 VARIABLE : PQVAR / PVAR
             FILENAME : ssh.nc
             TIME     : 16-DEC-1992 12:00 to 16-DEC-2012 00:00
          0.001568

'list intercep'
  VARIABLE : QAVE - SLOPE*PAVE
             FILENAME : ssh.nc
             TIME     : 16-DEC-1992 12:00 to 16-DEC-2012 00:00
         -41.19

'list rsquare'
 VARIABLE : (PQVAR*PQVAR) / (PVAR*QVAR)
             FILENAME : ssh.nc
             TIME     : 16-DEC-1992 12:00 to 16-DEC-2012 00:00
          0.4646

Then I check this simple calculation using an MS-Excell.
I found that the slope and intercept are different. Only RSQUARE is showing the similar result.
What I got in MS-Excell is:

slope = 0.0477
intercept = 69.284

And I think the results from MS-Excell are correct.

Any idea how to solve it?
Thanks.

Iskhaq

---------------------------------------------------------------- Dr. Iskhaq Iskandar Jurusan Fisika, Fakultas MIPA Universitas Sriwijaya Kampus Inderalaya, Ogan Ilir (OI) Sumatra Selatan, 30662 INDONESIA Phone: +62 (711) 580743 Fax: +62 (711) 580268 E-mail: iskhaq.iskandar@xxxxxxxxx http://iskhaq.wordpress.com/ ----------------------------------------------------------------

Attachment: ssh.nc
Description: Cdf file


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