set.seed(123);
x=rnorm(10, mean = 2, sd = 5)

LikeNormUnivar<-function(param,data){
  mu=param[1];
  sdev=param[2];
  densityvector=dnorm(data, mean = mu, sd = sdev, log = FALSE)
  like=prod(densityvector)
  return(-like)
}

theta.start = c(2,4)
ans = optim(par=theta.start, fn=LikeNormUnivar, data=x,control=list(trace=TRUE),
            method="BFGS")
ans$par