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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 ararix[/i] [br]Origin Ver. and Service Release (Select Help-->About Origin): Operating SystemOrigin Ver. and Service Release (Select Help-->About Origin): Operating System:Window 7 Hi, I am trying to fit my peak functions double sided exponentials. y(x) = A*Exp(-|x-x0|/xc) To consider Gaussian broadening of the peak induced by the experimental system. I used Integral functions Integration variable:t Argument : x, IRF, x0 , xc Return exp(-(x-t)^2/(2*IRF^2))*exp(-abs(t-x0)/xc); Also defined the main functions and parameters as below. Parameters : A=1, IRF=0.1, x0=0, xc=3, Integral elements : Lower lmt = -inf, upper lmt : inf x=x, IRF=IRF, x0=x0, xc=xc Main function y= A*integral(Integral, -inf ,inf ,x ,IRF ,x0, xc) With this fitting, the function fit the data, but the fitted curve has several regions with a null value (0). Therefore, the fitted curve looks discrete. As shown below (the actual data and fitting functions are more complicate than I describe above, but basically the same.) These null points disappear if I increase the IRF value from 0.1 to 0.5. So I guess this phenomena are affected by some integration time steps. Could you let me know what causes this and how can I solve this unexpecting discontinuity fitted curve with integral functions? [img]http://www.originlab.com/ftp/forum_and_kbase/Images/Graph22312.png[/img]: [/quote]   Check here to include your profile signature. Check here to subscribe to this topic.