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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 espenhjo[/i] [br]Hi, I am making a function in Origin C that is to be used in NLSF. I have called it [b]parplane[/b]. The actual function builds a damped oscillating curve that is a sum of n equations. I have declared this in [b]dSum[/b]. For each part in dSum roots exist that have to be found. These are found in the while loop and ascribed to rtn[i]. The parameters that are to be found with NLSF are a, I0 and C, from which a is the interesting one. The variable of the datasets is q. Now, a exists both in the rootfinding function and in dSum. Have I set up the script correctly so that NLSF optimalizes both the fit and the roots? Here is the script: #define JMAX 50 #define xacc 1e-12 #define nr_roots 100 //number of roots to be found double parplane(double a, double q, double I0, double C) //function for use in NLSF double dSum = 0; //cumulative output set to zero //void newt02() //{ double rtn[nr_roots],x1[nr_roots],x2[nr_roots],fx[nr_roots],df[nr_roots],dx[nr_roots]; int j; int i = 0; //these guess for the range in which a root exists could come from a //bracketing and bisection algorithm while (i < nr_roots) { x1[i] = (i+1)*PI-1; x2[i] = (i+1)*PI+1; rtn[i] = 0.5*(x1[i]+x2[i]); //first guess as the midpoint of the interval [x1,x2] for (j=1;j<JMAX; j++) { fx[i] = rtn[i] * tan(rtn[i]) / a; //the function with roots df[i] = tan(rtn[i]) / a + rtn[i] * (1+tan(rtn[i]) * tan(rtn[i])) / a; //first derivative of the function dx[i] = -fx[i]/df[i]; rtn[i] += dx[i]; printf("%e\n", dx[i]); if ((x1[i]-rtn[i])*(rtn[i]-x2[i]) < 0.0){ printf("error, jumped outside bounds"); exit(1);} if (fabs(dx[i]) < xacc){ printf("found root after %d attempts, at %lf\n", j, rtn[i]); i++; //exit(0); break;} if (j = JMAX - 1){ printf("error - exceeded max tries no root"); i++; break;} } } //exit(0); //} for (int k = 0; k < nr_roots; k++) { dSum += exp(-(rtn[k]^2) / (a^2)) * 2 * (1 + sin(2*rtn[k])/(2*rtn[k]))^(-1) * ((2*PI*q*a)*sin(2*PI*q*a)*cos(rtn[k])-rtn[k]*cos(2*PI*q*a)*sin(rtn[k]))^2 / ((2*PI*q*a)^2-rtn[k]^2)^2 ; } return I0 * dSum +C ; } Thanks! Espen [/quote]   Check here to include your profile signature. Check here to subscribe to this topic.