[R] Exponential fit of form y=exp(a*x) and not of form y=l*exp(a*x)

Ben Bolker bbolker at gmail.com
Sun Oct 23 19:02:24 CEST 2011

Henri Mone <henriMone <at> gmail.com> writes:

> I want to fit to my data an exponential function with following 
> functional form:
> y=exp(a*x)
> I used the function "nls" but this gives me exponential fits with
> following functional form:
> y=l*exp(a*x)
> With "l" being an scaling factor. What do I need to change in my R code?
> t.dataFitModel=nls(t.dataForFitY ~exp(a*t.dataForFitX),
> data=t.dataForFit, start=list(a = 0.01242922), trace=TRUE, algorithm =
> "plinear") 

  Use an algorithm other than "plinear", I think (admittedly this
is not at all clear from ?nls -- you would really have to go to the
references to find out).

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