| MPFITFUN Problem [message #44896] |
Fri, 22 July 2005 14:55  |
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Sean[1]
Messages: 11
Registered: July 2005
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Junior Member |
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Hello
I am having a problem with MPFITFUN. The code executes okay, but one
of the parameters that I put into the program does not ever change...
I know this is alot of text, but here's the output I receive on the
screen....
IDL> imodfit
Iter 1 CHI-SQUARE = 16.926937 DOF = 3
P(0) = 0.0250000
P(1) = 75.0000
Iter 2 CHI-SQUARE = 16.857964 DOF = 3
P(0) = 0.0250000
P(1) = 76.9480
Iter 3 CHI-SQUARE = 16.855946 DOF = 3
P(0) = 0.0250000
P(1) = 77.0617
Iter 4 CHI-SQUARE = 16.855669 DOF = 3
P(0) = 0.0250000
P(1) = 77.0102
Iter 5 CHI-SQUARE = 16.855644 DOF = 3
P(0) = 0.0250000
P(1) = 77.0369
Iter 6 CHI-SQUARE = 16.854858 DOF = 3
P(0) = 0.0250000
P(1) = 77.0236
Iter 7 CHI-SQUARE = 16.854755 DOF = 3
P(0) = 0.0250000
P(1) = 77.0235
Iter 7 CHI-SQUARE = 16.854755 DOF = 3
P(0) = 0.0250000
P(1) = 77.0235
% Program caused arithmetic error: Floating underflow
IDL>
As you can see, the parameter P(0) does not change. ...If I change the
order of the parameters, or the value of P(0), that value is still
unaffected! I have included the code I use below. As is evident, P(0)
IS used in the user-supplied function 'eval_pp2fvsimod', and it does
affect the output of that function. Any thoughts... anyone?
Thanks,
Sean
PRO imodfit
;Take the imod test data and fit to it to try and find the modulation
;conversion
;restore, '~/windows/CLHCalibrations/imodtest/imod123.sav'
pp2ftestshort = [0.000411136, 0.000483014, 0.000574490, 0.000626735,
0.000630612]
imodtestshort = [.5, 1., 1.5, 2, 2.5]
;need to scale the pp2f values to rcalb = 10.5. ...value used was 21
pp2ftestshort = pp2ftestshort * 21. / 10.5
weights = .2*pp2ftestshort
vmrguess = 75.
omegaguess = .025d ;guess for the conversion, cm^-1 / mA
params = [omegaguess, vmrguess]
result = mpfitfun('EVAL_pp2fvsimod', imodtestshort, pp2ftestshort,
weights, params, yfit=fitval, perr=perr)
END
function eval_pp2fvsimod, x,a
pmod = a[0] * x * 29979.
ihm = 2 ;ihm=2 means second harmonic
sr = 1. ;scan range, in cm-1
res = 10. ;resolution, in MHz
npts = sr * 29979.246 / res ;number of points in frequency and
transmission arrays
f1 = 7306.252 ;start frequency of scan, in cm-1
dlt = res / 29979.246
frq = f1 + findgen(npts)*dlt ;frequency array, in cm -1
pressure = 312. / 1013.
make_line, pressure, a[1], frq, trans=t3
t3 = reform(t3)
pp2freturn = fltarr(n_elements(x))
FOR i = 0, n_elements(x)-1 DO begin
der2f, frq, t3, npts, res, ihm, pmod[i], t2, pratio, zlobe
pp2freturn[i] = pratio
ENDFOR
return, pp2freturn
END
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