I want to thank professor Tura for his help but the function in some cases
fails to converge and I am not able to
understand the reason :
> GAS
[1] 0.8108649 1.0386906 1.1638837 2.4144286
> PRESSURE
[1] 0 5 15 45
> model.1 <- nls(GAS_PER_G ~ SSlogis(PRESSURE, ASym, xmid, scal))
model.1 <- nls(GAS_PER_G ~ SSlogis(PRESSURE, ASym, xmid, scal))
Error in nls(y ~ 1/(1 + exp((xmid - x)/scal)), data = xy, start = list(xmid =
aux[1], :
step factor 0.000488281 reduced below 'minFactor' of 0.000976562
>
Massimo Cressoni
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