lsqcurvefit constrain to real fitting parameters

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Rosalie
Rosalie 2012-5-15
Hi,
I'm trying to fit my data using the 'lsqcurvefit' command. However this returns me imaginairy fitting parameters, which I don't want. Is there any way to constrain the fitting parameters to real numbers?
The function I'm trying to fit is the following:
function F = eWLC(pp,y)
F = pp(2)*(1-1/2*sqrt(((4.1)./(y-pp(4))./pp(1)))+(y-pp(4))./pp(3));
thanks,
Rosalie

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回答（1 个）

Adam Parry
Adam Parry 2012-6-28
I'm sorry that I don't have an answer but I am also suffering from the same problem.
Did you come up with a fix, or was it to do with the equation itself?
  1 个评论
Star Strider
Star Strider 2012-6-28
编辑：Star Strider 2012-6-28
From a quick look, it would seem that constraining
pp(4) < y
might keep everything real, but without knowing more I can't be sure.
What are the parameter value estimates that 'lsqcurvefit' returns? Are the complex parameter estimates conjugates? How well does the resulting function fit the data?

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