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strinh

1 Posts
Posted - 07/16/2015 :  07:57:31 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Ver. 9 and Service Release (Select Help-->About Origin):
Operating System: Win7

Hi I found an article that references originlab to solve a equation for the binding constant given absorbance values. the article provides the script that was used (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2881600/):

A=K1*K2;

B=K1+2*K2*K1*Ht-K1*K2*x;

C=1+K1*Ht-K1*x;

D=-x;

for (G=x, step=1; abs(step)>1e-15; G=G-step){

step=(a*G*G*G+b*G*G+c*G+d)/(3*a*G*G+2*b*G+c);};

y=Ht*(E0+E1*K1*G+E2*K1*K2*G*G)/(1+K1*G+K1*K2*G*G)


I am new to origin; and looked online for tutorials and I have gathered that I need to make a user-defined fit; but im not sure how to implement the script. I tried to type in the code (lab talk) into the user-defined wizard but when it came down to executing the fit; it failed all datasets; I think im not sure what needs to be done. the scatter plot is correct; but the fit is just a straight line. please any help would be appreciated; thanks

easwar

USA
1964 Posts
Posted - 07/16/2015 :  2:36:45 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi strinh,

In the paper they state:
"In order to address this problem and avoid as many assumptions as possible, we have developed a method that combines an in-house written subprogram (“script”) with the nonlinear curve fitting operation of Origin. This method allows us to determine iteratively the parameter values in the relevant isotherms that best fit the experimental data"

So it looks like they have developed some custom LabTalk script in Origin, in addition to defining a fitting function.

I suggest you contact the authors and ask if they can provide the script and the fitting function to you?

Easwar
OriginLab
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