[R] Use of optim to fit two curves at the same time ?

[Arnaud Mosnier]

Dear list,

Here is a small example code that use optim and optimize in order to fit
two functions.
Is it possible to fit two functions (like those two for example) at the
same time using optim ... or another function in R ?

Thanks

Arnaud

######################################################################
## function 1
x1 <- 1:100
y1 <- 5.468 * x + 3 # + rnorm(100,0, 10)
dfxy <- cbind(x1,y1)

# Objective function
optfunc <- function(x, dfxy){
  a <- x[1]
  b <- x[2]
  xtest <- dfxy[,1]
  yobs <- dfxy[,2]
  ysim <- a*xtest + b
  sum((ysim - yobs)^2)
}

out<- optim(par=c(0.2,5), fn=function(x){optfunc(x, dfxy)}, method =
"Nelder-Mead", hessian = F)


## function 2

x2 <- seq(0.01, 0.1, length=100)
y2 <- exp(30*x2)
dfxy2 <- cbind(x2,y2)

# objective function
optfunc2 <- function(x, dfxy){
  a <- x[1]
  xtest <- dfxy[,1]
  yobs <- dfxy[,2]
  ysim <- exp(a*xtest)
  sum((ysim - yobs)^2)
}

out<- optimize(f=function(x){optfunc2(x, dfxy2)}, interval=c(0,500))

######################################################################

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