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2012 Apr 17
3
error using nls with logistic derivative
...(b-x)/c)) (this is the parametrization for the SSlogis function with nls) The derivative calculated with D function is: > logis<- expression(a/(1+exp((b-x)/c))) > D(logis, "x") a * (exp((b - x)/c) * (1/c))/(1 + exp((b - x)/c))^2 So I enter this expression in the nls function: ratelogis <- nls(Y ~ a*(exp((b-X)/c)*(1/c))/(1 + exp((b-X)/c))^2, start=list(a = 21.16322, b = 8.83669, c = 2.957765), ) The data is: > Y [1] 5.5199668 1.5234525 3.3557000 6.7211704 7.4237955 1.9703127 [7] 4.3939336 -1.4380091 3.2650180 3.5760906 0.2947972 1.0569417 > X [1] 1 0...