n2gaussfit not fitting all parameters … why?

Lowell Tacconi-Garman wrote on Jun 29, 2010

Perhaps I'm doing something stupid, but I'm having a problem with n2gaussfit in that it doesn't seem to fit all the parameters. Specifically, it seems that FWHM, Ellip., and Theta remain constant for all fitting that I do. Below you will find my params for n2gaussfit and tgausspars. Following that are three example input lines and their corresponding output values. Any ideas why this is failing?

fitting> lpar n2gaussfit

input = "cont_Pm180[258:278,966:986]" >image(s) to fit
output = "n2gaussfit.db" >output table
(rt = no) >get initial guess from table ?
(tablein = "") >table with initial guess
(row = 1) >row from which to take initial guess
(tgausspars = "") >pset for 2-d Gaussian
(errorpars = "") pset for error-related parameters
(controlpars = "") pset for algorithm control parameters
(verbose = yes) >display results ?
(averbose = yes) >display iteration info ?
(version = "05May91") >date of installation
(mode = "al")

fitting> lpar tgausspars

(a = 0.) >initial guess for background
(ampl = INDEF) >initial guess for peak amplitude
(xcent = INDEF) >initial guess for X center position
(ycent = INDEF) >initial guess for Y center position
(fwhm = INDEF) >initial guess for fwhm
(ellip = INDEF) >initial guess for ellipticity
(theta = INDEF) >initial guess for position angle (degrees)
(boxsize = 21) >box size
(va = yes) >vary background ?
(vampl = yes) >vary amplitude ?
(vxcent = yes) >vary X center ?
(vycent = yes) >vary Y center ?
(vfwhm = yes) >vary fwhm ?
(vellip = yes) >vary ellip ?
(vtheta = yes) >vary theta ?
(version = "12Jul90") >date of installation
(mode = "h")

To illustrate the point, the three lines:

n2gaussfit(input="line+cont_Pm180[430:450,106:126]",output="n2gaussfit.db")
n2gaussfit(input="line+cont_Pm180[633:653,047:067]",output="n2gaussfit.db")
n2gaussfit(input="line+cont_Pm180[502:522,502:522]",output="n2gaussfit.db")

produce

fitting> prfit n2gaussfit.db

Original file: line+cont_Pm180[430:450,10
Time: Mon 15:08:36 28-Jun-2010
Row: 38
Function: twodgaus chi-square: 20.01 rms: 4.507928
Units: Auto npts: 441
Ampl. = 16.08 X = 10.96 FWHM = 0.2
Back. = -3.712 Y = 10.95 Ellip = 0.1
Ang. = 1146.

Original file: line+cont_Pm180[633:653,04
Time: Mon 15:08:36 28-Jun-2010
Row: 39
Function: twodgaus chi-square: 13.8 rms: 3.743816
Units: Auto npts: 441
Ampl. = 12.65 X = 10.99 FWHM = 0.2
Back. = -2.864 Y = 11.97 Ellip = 0.1
Ang. = 1146.

Original file: line+cont_Pm180[502:522,50
Time: Mon 15:08:36 28-Jun-2010
Row: 40
Function: twodgaus chi-square: 59409. rms: 245.6183
Units: Auto npts: 441
Ampl. = 2076. X = 11.01 FWHM = 0.2
Back. = 15.14 Y = 11. Ellip = 0.1
Ang. = 1146.

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Last post on Jun 29, 2010