[R] nls and four parameter estimates

Hello all! I am trying to estimate four parameters (mu, sigma, theta and lambda) of a model Using the nls package in R, I can only get it to work if I limit the number of parameters to be estimated to three (i.e. mu, sigma and theta) as in the first model - mod1 - below. Including a fourth param

[R] Estimating Four Parameters with nls in R

Hello all! I am trying to estimate four parameters of a model (mu, sigma, theta and lambda) for a subset of data (snapshot given below). I have tried to do this using the nls package in R but I kept getting error messages (Error in numericDeriv(form[[3L]], names(ind), env) : --AND-- Missing va