
Applied Math Applied Math Forum 
 LinkBack  Thread Tools  Display Modes 
February 12th, 2009, 03:11 AM  #1 
Newbie Joined: Feb 2009 Posts: 1 Thanks: 0  fit one nonlinear function to four datasets
Dear all, I encountered a math problem when trying to find a set of robust and accurate parameters for a PDF, a nonlinear function with 3 parameters. The problem is: I have 4 datasets (X1,Y1), (X2,Y2),(X3,Y3),(X4,Y4) for a certain distribution. Each set, (Xi, Yi), contains about 400 data and was obtained from a different observational experiment. So it is assumed that different datasets should have different error variance. I am trying to use nonliner regression to obtain an empirical function from the four data sets. As the variance in each data set is unknown, it is impossible to obtain a weighting coefficient if i put them together. Is there any other solution for this case ? The empirical function is a*X^b/(1+exp(c*X)). I will appreciate very much if some could give me some support. Thank you! Sam 

Tags 
datasets, fit, function, nonlinear 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Applying proportional relationships between datasets  Rincewind  Applied Math  3  March 4th, 2014 12:30 PM 
Comparing three datasets and two variables at the same time?  Spoilerman  Algebra  0  July 5th, 2013 08:13 AM 
nonlinear DE  elimax  Calculus  3  July 7th, 2011 03:28 AM 
nonlinear regression  method_man  Applied Math  3  June 28th, 2011 11:20 AM 
nonlinear function  wannabe1  Linear Algebra  2  February 2nd, 2010 10:56 PM 