[R] Coefficient of Determination for nonlinear function

[Uwe Wolfram]

Dear Subscribers,

I did fit an equation of the form 1 = f(x1,x2,x3) using a minimization
scheme. Now I want to compute the coefficient of determination. Normally
I would compute it as

r_square = 1- sserr/sstot with sserr = sum_i (y_i - f_i) and sstot =
sum_i (y_i - mean(y))

sserr is clear to me but how can I compute sstot when there is no such
thing than differing y_i. These are all one. Thus mean(y)=1. Therefore,
sstot is 0. 

Thank you very much for your efforts,

Uwe

-- 
Uwe Wolfram
Dipl.-Ing. (Ph.D Student)
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Center of Musculoskeletal Research Ulm
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