All Forums  Origin Forum  Origin Forum  [SOLVED] Fitting custom-function does not converge

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Screensize: 640 x 480 800 x 600 1024 x 768 1280 x 1024 UserName: Password: Anti-Spam Code: Format Mode: Basic  Help  Prompt  Format: Font Andale Mono Arial Arial Black Book Antiqua Century Gothic Comic Sans MS Courier New Georgia Impact Lucida Console Script MT Bold Stencil Tahoma Times New Roman Trebuchet MS Verdana   Size 1 2 3 4 5 6   Color Black Red Yellow Pink Green Orange Purple Blue Beige Brown Teal Navy Maroon LimeGreen Message: * HTML is OFF * Forum Code is ON Smilies [quote][i]Originally posted by ue0405[/i] [br]Dear All, I am sorry to bother you with a (hopefully?) quickly answered to problem: I have xdata = x and ydata = y and try to fit the following equation, which I entered as custom-made and explicit: independent variable: x dependent variable: y parameters: k_a,m_0,k_d function form: Oritin C function: y = k_a*m_0*2.686/(k_a*2.686+k_d)*(1-exp(-(k_a*2.868+k_d)*x)) The function does initiate when I compile it. I plug in startvalues for all three parameters although I am not 100% that they are correct, but should be in the same order of magnitude. After a short time after trying to fit I receive the error that the [red]"fit does not converge - reason unknown. Fitting was done with weights. Check weighting method and error bar values for inconsistency or repeat fitting without weighting."[/red] I translated this error from German, possibly there are some minor deviations to the original message but the meaning should be clear. I did check the datasets and tryed others as well. It seems to be something integrally wrong with my programming. Any suggestions what I could try? Please dont hesitate if there is information missing. Origin Ver. and Service Release (Select Help-->About Origin): OriginPro 2015G (64-bit) Sr2 / b9.2.272 (Home Use) Operating System: Windows 7 Pro SP1 Best wishes Ulrich [/quote]   Check here to include your profile signature. Check here to subscribe to this topic.