Fitcoords

Tae-Soo Pyo wrote on Oct 22, 2004

Dear,

The 'order' of equation in IRAF means the number of terms (or coefficients) in the equation.
So the real order of equation is {('order' of IRAF') - 1}.  
For example, y = ax^2 + bx + c (ORDER: 3 in IRAF, 2 in mathematics).
If you set the xoder = 4, yorder = 3, the number of coefficients will be 4 x 3 = 12.

Best wishes,

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`
Tae-Soo Pyo 
Subaru Telescope
650 North A'ohoku Place, Hilo, HI 96720, USA 
Phone: +1(808)934-5951, FAX: +1(808)934-5983
E-mail: pyo@subaru.naoj.org
URL: http://www.naoj.org/staff/pyo
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`

----- Original Message -----
From: irafmail-gateway@noao.edu (Davey, Jeremy)
Date: Tuesday, October 19, 2004 4:50 am
Subject: Fitcoords

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> % mail adass-iraf-applications@iraf.noao.edu
> 
> I am trying to access the polynomial coefficients produced by the =
> fitcoords application in order to try to plot the distortion that =
> fitcoords has mapped.  However I find that the number of 
> coefficients is =
> less than expected for given x and y orders.  In my particular 
> case, =
> xorder =3D 4 yorder =3D 3, so I expect 20 coeffs.  But the fc file 
> has =
> only got 12 coeffs.  Is this actually a problem with fitcoords or 
> am I =
> just missing something?=20
> 
> Thanks
> 
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> <P><FONT SIZE=3D2> % mail adass-iraf-applications@iraf.noao.edu<BR>
> <BR>
> I am trying to access the polynomial coefficients produced by the =
> fitcoords application in order to try to plot the distortion that =
> fitcoords has mapped.  However I find that the number of =
> coefficients is less than expected for given x and y orders.  In 
> my =
> particular case, xorder =3D 4 yorder =3D 3, so I expect 20 coeffs. 
> =
> But the fc file has only got 12 coeffs.  Is this actually a 
> problem =
> with fitcoords or am I just missing something?<BR>
> <BR>
> Thanks</FONT>
> </P>
> 
> </BODY>
> </HTML>
> ------_=_NextPart_001_01C4B5C9.07F8C060--
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Michael C. B. Ashley wrote on Oct 22, 2004

Hi folks,

> The 'order' of equation in IRAF means the number of terms (or
> coefficients) in the equation.

It would be good if the "help" documentation, and the parameter
descriptions, in IRAF could be changed to reflect this. It has caused me
some confusion before.

Cheers,
Michael
--
A/Prof. Michael Ashley                      Department of Astrophysics
University of New South Wales        http://www.phys.unsw.edu.au/~mcba

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Last post on Oct 22, 2004