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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 tskisiu[/i] [br]Origin Ver. and Service Release (Select Help-->About Origin): 8.1SR3 Operating System: WinXP I would be very grateful if someone could help me with the following problem: I am fitting : [img]http://www.originlab.com/ftp/forum_and_kbase/Images/Naamloos.jpg[/img] my function has three fitting parameters: R, L, I0 the code is as follows: #pragma warning(error : 15618) #include <origin.h> #include <oc_nag8.h> struct user { double R, L, fitX; }; static double NAG_CALL f_callback(double alfa, Nag_User *comm) { struct user *sp = (struct user *)(comm->p); double R_2,L_2, fitX, Rdependent, Ldependent,cylinder; R_2=sp->R; L_2=sp->L; fitX=sp->fitX; Rdependent=2*J1(fitX*R_2*sin(alfa))/(fitX*R_2*sin(alfa)); Ldependent=sin(0.5*fitX*L_2*cos(alfa))/(fitX*L_2*cos(alfa)); cylinder=Rdependent*Ldependent*Rdependent*Ldependent*sin(alfa); return (cylinder); } //---------------------------------------------------------- // void _nlsfCylinderFormFactor( // Fit Parameter(s): double I0, double R, double L, // Independent Variable(s): double x, // Dependent Variable(s): double& y) { // Beginning of editable part double epsabs = 0.00001, epsrel = 0.0000001, result, abserr; Integer max_num_subint = 100; Nag_QuadProgress qp; static NagError fail; Nag_User comm; struct user s; s.R = R; s.L = L; s.fitX = x; comm.p = (Pointer)&s; d01sjc(f_callback, 0.0, PI/2.0, epsabs, epsrel, max_num_subint, &result, &abserr, &qp, &comm, &fail); if (fail.code != NE_INT_ARG_LT && fail.code != NE_BAD_PARAM && fail.code != NE_ALLOC_FAIL) { NAG_FREE(qp.sub_int_beg_pts); NAG_FREE(qp.sub_int_end_pts); NAG_FREE(qp.sub_int_result); NAG_FREE(qp.sub_int_error); } y = I0*result; } I am using integrator d01sjc to integrate f_callback over all alpha range, and it works very well. Now, I would like to introduce function w(L) so that the total fitting expression is: [img]http://www.originlab.com/ftp/forum_and_kbase/Images/Naamloos2.jpg[/img] How should I do it? I would be grateful for any suggestions, but a code example would be best. [/quote]   Check here to include your profile signature. Check here to subscribe to this topic.