quote:

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Originally posted by metalnonmetal

Hi I need to fit an equation like

(a^m)*((1-a)^n)*(-ln(1-a)^p)= b*A*integral(exp(-E/(RT))[lower limit, upper limit, dT)

I need to fit these from my data table of (a vs T) and the parameters are (m, n, p, A). (b,E,R) are constants

Please help

metalnonmetal

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	LT_execute("double xb;");
	LT_set_var( "xb", x );
	
	
	string strLT;
	strLT = "function double MyIntegrand(double u) { return exp(-17.68e3/(8.314*u)); }; double yb; yb = integral(MyIntegrand,1020.79,xb);";
	
	LT_execute(strLT);
	
	
	double y2;
	LT_get_var( "yb", &y2 );
	
	
	
	f=A*y2-(w^m)*((1-w)^n)*(-ln(1-w)^p)

	LT_execute("double xb;");
	LT_set_var( "xb", x );
	
	
	string strLT;
	strLT = "function double MyIntegrand(double u) { return exp(-17.68e3/(8.314*u)); };	double yb;	yb = integral(MyIntegrand,1020.79,xb);";
	
	LT_execute(strLT);
	
	
	double y2;
	LT_get_var( "yb", &y2 );
	
	
	
	f=0.05*A*y2-(w^m)*((1-w)^n)*((-ln(1-w))^p);

quote:

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Originally posted by JacquelineHe

Hi

We checked the code again, and I am not sure whether you miss a () for the (-ln(1-a)^p). I added the () , fixed some problem and change the prameters again. Please try this function body code again.

	LT_execute("double xb;");
	LT_set_var( "xb", x );
	
	
	string strLT;
	strLT = "function double MyIntegrand(double u) { return exp(-17.68e3/(8.314*u)); };	double yb;	yb = integral(MyIntegrand,1020.79,xb);";
	
	LT_execute(strLT);
	
	
	double y2;
	LT_get_var( "yb", &y2 );
	
	
	
	f=0.05*A*y2-(w^m)*((1-w)^n)*((-ln(1-w))^p);

Then set the parameter to:
m=0.5, n=0.5, p=0.5, A=0.01

If you want to keep m and n at the range of 0 to 1, then you can set their Bounds to 0<m<1 and 0<n<1.

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Then select you dataset and choose menu Analysis:Fitting:Nonlinear Implicit Curve Fit to open the dialog.

1> Choose your defined function.
2> Go to the Fitted Curvespage under Setting tab. In the right panel, set Data Type of x to Fitted Point for Input Data
3> Fit the Function again.

Thanks
Jacqueline
OriginLab

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