| Re: MPFITFUN error -- only reading the first data value [message #90714 is a reply to message #90711] |
Thu, 02 April 2015 02:16   |
graham kerr
Messages: 5
Registered: March 2015
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Junior Member |
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Hi,
Yes, that was a typo (but wasn't in my actual code).
start_temp is a float (or double) not a 1-element array so I don't think that's where the error is unfortunately.
On Wednesday, April 1, 2015 at 7:14:08 PM UTC+1, Jeremy Bailin wrote:
> On Tuesday, March 31, 2015 at 5:45:03 PM UTC-5, graham kerr wrote:
>> Hello everyone,
>>
>> I am trying to use mpfitfun to fit data observed at multiple wavelengths to a blackbody function, with temperature as the only variable; so I'm trying to find the best fit temperature.
>>
>> My function is called planck_fit_sot.pro, and is below. When I use mpfitfun the output has clearly only tried to fit the first data point. For a few test runs where I simulated blackbody intensities at multiple wavelengths (100 in total), the fitting routine returns the temperature that I set the first data point to. Also, yfit has only one value (the first), with all the rest '0'.
>>
>> Does anyone know what (presumably silly) mistake I've made here, and why mpfitfun is not using all the data to fit the function?
>>
>> cheers,
>> Graham
>> _____________________________
>>
>> mpfitfun procedure where wave_rgb & data_rgb are input and temp_range and start_temp are included as optional input :-
>>
>> if n_elements(start_temp) eq 0 then start_temp = double(6000.0)
>> parinfo = {value:0.0, fixed:0, limited:[0,0], limits:[0.0,0.0]}
>> parinfo[0].value = start_temp
>> parinfo[0].fixed = 0
>> if n_elements(temp_range) eq 0 then begin
>> parinfo[0].limited(*) = 0
>> endif else begin
>> parinfo[0].limited(*) = 1
>> parinfo[0].limits[0] = temp_range[0]
>> parinfo[0].limits[1] = temp_range[1]
>> endelse
>>
>> fit_fn = mpfitfun('planck_fit_sot', wave_rgb, data_rgb, err, $
>> parinfo = parinfo, double = double,$
>> maxiter = 2000, bestnorm = bestnorm,$
>> yfit = yfit, perror = perror, dof = dof,$
>> status = status, errmsg=errmsg)
>> _____________________________
>>
>> planck_fit_sot.pro :-
>>
>> FUNCTION planck_fit_sot, wave, temp
>>
>> ;Some constants
>> cc = 2.99792458d10 ;cm/s
>> hh = 6.62606957d-27 ;erg s
>> kb = 1.3806488d-16 ;erg/K
>>
>> wave_cm = wave/1.e8 ;cm
>>
>> bb_fn = dblarr(n_elements(wave))
>>
>> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;
>> ;;;;;;;;;;; DEFINE THE FUNCTION ;;;;;;;;;
>> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;
>>
>> ;2*h*c^2.0
>> const1 = double(2*hh*cc*cc)
>>
>> ;h*c/k
>> const2 = double(hh*cc/kb)/wave_cm
>>
>> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;
>>
>> bb_fn = const1 / ( wave_cm^5.0 * ( exp( const2]/temp)-1. ) )
>>
>> bb_fn = bb_fn*1.d-8 ;ergs/s/cm^2/sr/Ang
>>
>> bb_fn_watts = bb_fn/1.e7 ;W/cm^2/sr/Ang
>> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;
>>
>> return, bb_fn_watts
>>
>> end
>
>
> As written it won't compile -- I'm guessing the "]" isn't supposed to be here:
>
> bb_fn = const1 / ( wave_cm^5.0 * ( exp( const2]/temp)-1. ) )
>
> Assuming that's fixed, I would speculate that your start_temp variable coming into the function is an array (possibly a 1-element array) instead of a scalar. Try "help, start_temp" to check.
>
> -Jeremy.
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