[R] Help in optimization

[Ricardo Bessa]

I have had a problem in finding the minimum of a function, the function in 
cause is:

curv <- function(a,b){
date <- read.table("bessa.csv",header=T,sep=";",dec=",")
calP <- (22000)/(1+exp(-(a*date$v+b)))
err <- (calP-date$P)^2
return(sum(err))
}

It would like to know which function that I must use to find the values of 
“a” and “b” that minimize the function curv. I Already tried with the 
functions “optim” and “nlm”, but without success, perhaps I am not using 
them correctly.

Ricardo Bessa

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