Error in get(as.character(FUN), mode = "function", envir = envir) - r

Question

I am new to R, so forgive me if the question is a little silly.
I am trying to write a simple while loop for a value function iteration. My function (optim.routine) uses the solver ipoptr. Here is my code:
d<-1
old1<-0
old2<-0
num.iter<-0
i.esp<-1e-05
i.T<-100
lb<-0
ub<-10
while (d>i.eps & num.iter<i.T){
new1 <- optim.routine(old1, old2, eval_f=eval_f, eval_grad_f=eval_grad_f, lb=lb, ub=ub, update=FALSE)
d<-dist(c(old1, new1), method="euclidean")
num.iter<-num.iter+1
old1<-new1
}
where optim.routine is the following function:
optim.routine<-function(old1, old2, eval_f=obj, eval_grad_f=obj.deriv, lb=lb, ub=ub, update){
if (isTRUE(update)){
var2<-old2
var1<-old1
var1.deriv<-deriv(var1)
optimize <- ipoptr(x0 = old2, eval_f = eval_f, eval_grad_f = eval_grad_f, lb = lb,
ub = ub)
new1<- optimize$objective
new2<- optimize$solution
old2<-new2
old1<-new1
}else{
var2<-old2
var1<-old1
var1.deriv<-vf.deriv(var1)
optimize <- ipoptr(x0 = old2, eval_f = eval_f, eval_grad_f = eval_grad_f, lb = lb,
ub = ub)
new1<- optimize$objective
new2<- optimize$solution
old1<-new1
}
}
and deriv is a function that computes derivatives.
I get the following error if i try to run the code:
source('/mnt/ide0/home/myname/Documents/optim.R')
Error in get(as.character(FUN), mode = "function", envir = envir) :
object 'fn' of mode 'function' was not found
and if I debug the function:
Browse[2]> n
Error in isTRUE(update) : argument "update" is missing, with no default
If I only source the function without the while loop no error is displayed. Honestly, I have no clue. Any help is greatly appreciated. Thanks!
Claudia

Answer 1

I had exactly the same error message when I named a variable with the
same name of an existing function in R. I've found this tip
here: http://notepad.patheticcockroach.com/2565/a-bad-idea-in-r-using-variables-with-the-same-name-as-existing-functions/ Hope it helps you too.
– FraNut Oct 12 at 11:26
He's right refrain from using variables that might be function names too.
e.g
z1<-aggregate(steps ~ interval, data_df, mean)
mean<-mean(z[,2],na.rm = TRUE)
mean is a variable and a function name passed as an argument to the aggregate function causing a conflict

Answer 2

Many times that error will appear when you previously created an object called "mean" in the R environment. This creates a conflict when calling the function "mean". To stop this error use:
rm(mean)
This removes the object "mean" from the environment and allows R to call the function "mean".