I have a small reproducible version of the issue I'm having with my program.

The structure of my code involves nested functions, similar to the one shown below, only more complex.

x <- data.frame(c(1:5),c(0))
colnames(x) <- c("val1", "val2")

foo <- function() {
  for(i in 1:length(x[,1])) {
    bar(i)
  }
  print(x)
}

bar <- function(i) {
   if(x[i,2] == 0) {
    x[i,2] <- 1
    print(x[i,])
  }
  return(x)
}

>foo()
  val1 val2
1    1    1
  val1 val2
2    2    1
  val1 val2
3    3    1
  val1 val2
4    4    1
  val1 val2
5    5    1
  val1 val2
1    1    0
2    2    0
3    3    0
4    4    0
5    5    0

So as the results show, the value is not being returned from the bar() function in order to update the data frame.

What do I need to change in order to return an updated table to the foo() function?

Thanks in advance.

It's better to pass the data.frame as an argument instead of hard coding it to the function. Here are some modifications that should accomplish what you're looking for

foo <- function(df) {
  for(i in seq_len(nrow(df))) {
    df[i, ] <- bar(df[i, ])
  }
  print(df)
}

bar <- function(df) {
  if(df[, "val2"] == 0) {
    df[, "val2"] <- 1
    print(df[, ])
  }
  return(df)
}

> foo(x)
  val1 val2
1    1    1
  val1 val2
2    2    1
  val1 val2
3    3    1
  val1 val2
4    4    1
  val1 val2
5    5    1
  val1 val2
1    1    1
2    2    1
3    3    1
4    4    1
5    5    1

more