| T O P I C R E V I E W |
| gansy |
Posted - 09/03/2007 : 3:30:19 PM
Origin Version (Select Help-->About Origin): OriginPro 7.5
Operating System: WinXP
I've been attempting to curve fit some growth data to the built in Gompertz equation. However, it keeps giving me an error saying that either my data set is empty or the equation is wrong. When I tried the exact same data set with the logistic equation, it worked! Could there be something wrong with the built in Gompertz equation? I tried to enter the Gompertz in myself, but mine doesn't seem to fit right. Any suggestions?
In addition, does anyone know if Origin will determine the point of inflexion on the curve?
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| 2 L A T E S T R E P L I E S (Newest First) |
| gansy |
Posted - 09/04/2007 : 06:48:00 AM
Works now, great, thanks! |
| larry_lan |
Posted - 09/03/2007 : 10:55:11 PM
Hi Samantha:
Sorry, this is a bug because improper parameter initialization. To fix it, browse to \FitFunc folder of Origin .exe folder, open the file, GOMPERTZ.FDF, by some text editor, such as Windows Notepad. Go to the following section and change the red lines:
[Parameters Initialization]
sort( x_y_curve );
smooth( x_y_curve );
a = max(y_data);
x_y_curve = ln( x_y_curve );
x_y_curve = ln( ln(a) - x_y_curve );
double coeff[2];
fitpoly( x_y_curve, 1, coeff );
xc = -coeff[1] / coeff[0];
k = coeff[1] / xc;
as follow:
xc = -coeff[0] / coeff[1];
k = -coeff[1];
And Save to replace the original file. (You can make a backup before save.)
Thanks
Larry
OriginLab Technical Services |
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