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anildsx
Australia
Posts |
 Posted - 10/04/2006 : 06:11:25 AM
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Hi,
I have created a new (user-defined) Non-Linear Curve Fit function to fit my experimental values. In the equation used for fitting, I have some known values (defined as constants) and some unknown (variable). To get the guess values for the unknown, I am using MathCAD and use those guess values in Origin to fit the data. The simulation on my experimental data (in MathCAD) looks good, but as soon as I use simulated values (for unknown) in Origin in the defined function, the fit goes crazy and comes up with huge error-bars. There is no compilation error, so I assume the user-defined function is working well.
Thanks in advance!
The equations in Mathcad used for fitting is uploaded as a doc file and the origin script (main text) used is shown below,
Origin Script I wrote:
int i,
np,
maxq;
double ytemp,
term1Q,
term2Q,
D1Q,
D2Q,
P1Q,
P2Q,
EQ;
np=10; //number of points
maxq=6*10^4;
ytemp = 0;
for (i=0; i<=10; i+=1)
{
qi = 0.01 + (maxq/np)*i;
if (qi=Q)
{
term1Q = Df+Db+(1/(2.0*pi*Q)^2)*((1/tauf)+(1/taub));
term2Q = sqrt(((Db-Df+(1/(2.0*pi*Q)^2))*((1/taub)-(1/tauf)))^2+4.0/(((2.0*pi*Q)^2)^2*tauf*taub));
D1Q = 0.5*(term1Q-term2Q);
D2Q = 0.5*(term1Q+term2Q);
P2Q = (Pb*Db+Pf*Df-D1Q)/(D2Q-D1Q);
P1Q = 1-P2Q;
EQ = P1Q*exp(-(2.0*pi*Q)^2*D1Q*bigd)+P2Q*exp(-(2.0*pi*Q)^2*D2Q*bigd);
}
ytemp = EQ;
};
E= ytemp*1;
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Mike Buess
USA
3037 Posts |
Posted - 10/04/2006 : 08:04:46 AM
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The only mistake I see is the if condition, which should be qi==Q. Your function will compile and run with a single equal sign but will surely give the wrong result.
Mike Buess
Origin WebRing Member |
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anildsx
Australia
Posts |
Posted - 10/05/2006 : 05:00:04 AM
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Sorry I have to refine my question now!
How do I programme in Origin to get each value of EQ for every increment 'i'(which changes the value of Q)?
I mean in C-programme, at the end of 'for' loop I can include
printf("%lf",EQ);
printf("%lf",Q);
to get EQ for each value of Q. Is there a way to do the same in Origin?
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Mike Buess
USA
3037 Posts |
Posted - 10/05/2006 : 07:56:12 AM
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Also works in Origin... printf("%d: EQ=%f, Q=%f\n",i,EQ,Q)
But I don't see how the code you presented changes Q. Isn't Q the independent variable for fitting and E the dependent?
Mike Buess
Origin WebRing Member |
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anildsx
Australia
Posts |
Posted - 10/06/2006 : 01:11:11 AM
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Thanks Mike, now I sorted it out!
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Topic |
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Simulation vs Fitting- Error bars