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Last Post 12 Nov 2002 12:23 PM by  Jonathan Greenberg
Problems getting CURVEFIT to work...
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Jonathan Greenberg



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12 Nov 2002 12:23 PM
    Hi there, I'm trying to use CURVEFIT to fit data to a decay function of the form: f(x) = a(1-e^(bx))+c My code is as follows: pro decayfunc, X,A,F,pder bx=EXP(A[1]*X) F=A[0]*(1-bx)+A[2] if N_PARAMS() GE 4 THEN $ pder=[[1-bx],[-A[0]*X*bx],[replicate(1.0,N_ELEMENTS(X))]] end X=[30185.0,33897.0,35089.0,35377.0,35665.0] Y=[0.3002,1.3849,1.3004,1.226,1.3118] A=[1.25,-1.0,-0.1] weight=[1.0,1.0,1.0,1.0,1.0] yfit=CURVEFIT[X,Y,weights,A,SIGMA,FUNCTION_NAME='decayfunc',/DOUBLE] I get the error: CURVEFIT: Failed to converge- CHISQ increasing without bound. and the SIGMA values are: .44721360,Infinity,.44721360 The plot of the data looks like it should fit a decay equation, but CURVEFIT can't seem to determine the parameters. I've tried a number of different starting values for A to no avail. Any suggestions?

    Jonathan Greenberg



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    04 Dec 2002 04:57 PM
    monsieur vous avez oubliez de declarer vos variable de meme de faire un random volum
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