I tried to fit data with the following function: fit<-nls(y~ Is*(1-exp(-l*x))+Iph,start=list(Is=-2e-5,l=2.3,Iph=-0.3 ),control=list(maxiter=500,minFactor=1/10000,tol=10e-05),trace=TRUE) But I get only a singular Gradient warning... the data can by found attached(there are two sampels of data col 1/2 and 3/4).
I tried to fix it by chanching the start parameters but that didn't solve the problem. Would it be a possibiliti to use the selfstart Model? How? Thanks for any answers This
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