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fitting with SVDfit and curvefit
| fitting with SVDfit and curvefit [message #11138] |
Mon, 02 March 1998 00:00 |
Kirmanta de Malher
Messages: 5
Registered: March 1998
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Junior Member |
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Hi, everybody,
well i am testing several IDL functions to fit one dimensional data.
CURVEFIT
For the moment, i tested CURVEfit.
My datas are for example a lorentzian (e.g 1/(1+x*x) ) with 3
parameters.
With a 'real' lorentzian curve (without any other curves or offest),
Curvefit gave me the right results.
BUT, when i add an offset to the curve, then i obtained poor results.
I have the same results or errors due to the arithmetic errors (
overflow error,...) when my initial guess for the parameters are not
close to the theoritical ones.
SVDFIT
I would want an example to show me how i must create an user model
function to be used with SVDFIT.
This function may not be polynomial or linear.
AN example is :
a(0)^2/(a(0)^2*a(1) + 4 *(a(2) -x)^2)
I am using the 4.0.1 on a Sparc station
thansk for answering
prefer email to : fernande@irm.chu-caen.fr
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| Jesus Fernandez |
| Unite IRM du CHU de Caen |
| Avenue de la cote de nacre |
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| France |
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