I am currently working with a self-starting function for four parameters which I based on SSfpl but with a different formula.

This is the formula for my self-starting function:

(b1 * ((b2 * x)^b4)) / (1 + ((b2 * x)^b4))^(b3 / b4)

The code below is for SSfpl with a formula A + (B - A)/(1 + exp((xmid - input)/scal)):

ir <- as.vector(coef(lm(x ~ I(log(prop/(1-prop))), data = xy)))
pars <- as.vector(coef(nls(y ~ cbind(1, 1/(1 + exp((xmid - x)/ exp(lscal)))), 

data = xy,

start = list(xmid = ir[1L],
lscal = log(abs(ir[2L]))),
algorithm = "plinear"))
value <- c(pars[3L], pars[3L] + pars[4L], pars[1L], exp(pars[2L]))

I can't figure out how to set up the code above properly for my self-starting function. Any help is highly appreciated. Thank You.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.