Hi,
I was hoping to get some advice on how to derive estimates of slopes from four
parameter logistic models fit with SSfpl.
I fit the model using:
model<-nls(temp~SSfpl(time,a,b,c,d))
summary(model)
I am interested in the values of the lower and upper asymptotes (parameters a
and b), but also in the gradient of the line at the inflection point (c) which
I assume tells me my rate of increase when it is steepest (?).
However, I cannot work out how to derive a slope estimate. I'm guessing it has
something to do with the scaling parameter d but having searched the internet
for hours I have not made any progress, and it is probably quite simple. Any
help would be hugely appreciated!
All the best
Sam
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