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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 prathiba[/i] [br]Origin Ver. 8.0 and Service Release (Select Help-->About Origin): Operating System:windows 7 I tried to do the fit using the function Cv=a9Nk_B #12310;(x/#952;D)#12311;^3 #8747;_0^(#952;/x)#9618;#12310;dx (x^4 * e^x)/#12310;((e^x)-1)#12311;^2 #12311; I have written the program and compiled it. The compilation was successful. But I could not do the fitting using the function. Can anyone tell what is the problem? Thank you very much. ps: The function is given the end as a image. Define the Function Press F9 to open the Fitting Function Organizer and then create a new Category named FittingWithIntegral. Define a new fitting function nag_integration_fitting in the new category as follow: Function Name: nag_integration_fitting Function Type: User-Defined Independent Variables: x Dependent Variables: y Parameter Names: a Function Form: Origin C Function: Click the button (icon) beside the Function box to open the code builder and define and compile and save the fitting function as follows: #include <origin.h> // Add your special include files here. // For example, if you want to fit with functions from the NAG library, // add the header file for the NAG functions here. #include <oc_nag8.h> // Add code here for other Origin C functions that you want to define in this file, // and access in your fitting function. struct user // parameters in the integrand { double cons; }; // Function supplied by user, return the value of the integrand at a given x. static double NAG_CALL f_callback(double x, Nag_User *comm) { struct user *sp = (struct user *)(comm->p); double cons; // temp variable to accept the parameters in the Nag_User communication struct cons = sp->cons; return (x*x*x*x*exp(x))/((exp(x)-1)*(exp(x)-1)); } // You can access C functions defined in other files, if those files are loaded and compiled // in your workspace, and the functions have been prototyped in a header file that you have // included above. // You can access NLSF object methods and properties directly in your function code. // You should follow C-language syntax in defining your function. // For instance, if your parameter name is P1, you cannot use p1 in your function code. // When using fractions, remember that integer division such as 1/2 is equal to 0, and not 0.5 // Use 0.5 or 1/2.0 to get the correct value. // For more information and examples, please refer to the "User-Defined Fitting Function" // section of the Origin Help file. //---------------------------------------------------------- // void _nlsfnag_integration_fitting( // Fit Parameter(s): double a, // Independent Variable(s): double x, // Dependent Variable(s): double& y) { // Beginning of editable part // Through the absolute accuracy epsabs, relative accuracy epsrel and max_num_subint you can // control the precision of the integration you need // if epsrel is set negative, the absolute accuracy will be used. // Similarly, you can control only relative accuracy by set the epsabs negative double epsabs = 0.0, epsrel = 0.0001; // The max number of sub-intervals needed to evaluate the function in the integral // The more diffcult the integrand the larger max_num_subint should be // For most problems 200 to 500 is adequate and recommmended Integer max_num_subint = 300; // Result keeps the approximate integral value returned by the algorithm // abserr is an estimate of the error which should be an upper bound for the |I - result| // where I is the integral value double result, abserr; // The structure of type Nag_QuadProgress, // it contains pointers allocated memory internally with max_num_subint elements Nag_QuadProgress qp; // The NAG error parameter (structure) static NagError fail; // Parameters passed to integrand by Nag_User communication struct Nag_User comm; struct user s; s.cons = a; // Perform integration // There are 3 kinds of infinite boundary types you can use in Nag infinite integrator // Nag_LowerSemiInfinite, Nag_UpperSemiInfinite, Nag_Infinite d01smc(f_callback, 0, 444/x, epsabs, epsrel, max_num_subint, &result, &abserr, &qp, &comm, &fail); // you may want to exam the error by printing out error message, just uncomment the following lines // if (fail.code != NE_NOERROR) // printf("%s\n", fail.message); // For the error other than the following three errors which are due to bad input parameters // or allocation failure NE_INT_ARG_LT NE_BAD_PARAM NE_ALLOC_FAIL // You will need to free the memory allocation before calling the integration routine again to avoid memory leakage 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); } // Calculate the fitted value y = a*5.75*100000*(x/444)*(x/444)*(x/444)*result; // End of editable part } [img]http://www.originlab.com/ftp/forum_and_kbase/Images/Cv eqn for fit.png[/img] PRATHI [/quote]   Check here to include your profile signature. 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