How to avoid <<- by using assign

Question

I have two pieces of code I use often in which I use the <<- to assign to the Global environment from within a function. I know I should be using assign as it gives better control and is more predictable. I am trying to wrap my head around using assign but can't transfer the <<- code to code that uses assign:

A FAKE DATA SET AND THE TWO PIECES OF CODE WITH THE <<-

#CREATE A FAKE DATA SET
df <- data.frame(
    x.2=rnorm(25),
    y.2=rnorm(25),
    g=rep(factor(LETTERS[1:5]), 5)
)
#Use split to make a list of data frames
LIST <- split(df, df$g) #split it into a list of data frames
NAMES <- names(LIST) #save the names of this for later use 
LIST <- lapply(seq_along(LIST), function(x) as.data.frame(LIST[[x]])[, 1:2])

#THE TWO PIECES OF CODE THAT USE <<-
#Use Global Assignment to Change All Variable Names of Data Frames in a List
lapply(seq_along(LIST), function(x) names(LIST[[x]]) <<-
    unlist(strsplit(names(LIST[[x]])[1:length(names(LIST[[x]]))],
    ".", fixed=T))[c(T, F)]
)
LIST

#Rename All the Data Frames in the List Using Global Assignment
lapply(seq_along(LIST), function(x) names(LIST)[[x]] <<- NAMES[x])
LIST

My attempts to use assign:

lapply(seq_along(LIST), function(x) {
    assign(names(LIST[[x]]), 
    unlist(strsplit(names(LIST[[x]])[1:length(names(LIST[[x]]))],
    ".", fixed=T))[c(T, F)],  envir=.GlobalEnv)
    }
)
LIST

lapply(seq_along(LIST), function(x) assign(names(LIST)[[x]], 
    NAMES[x], envir=.GlobalEnv))
LIST

Please help me to do this correctly and axplain what is wrong with my approach. Thank you in advance.

Answer 1

I do not understand why you made this task so very complicated. Isn't this just:

LIST <- df[, 1:2]
names(LIST) <- sapply(strsplit(names(LIST), '.', fixed = TRUE), `[`, 1)
LIST <- split(LIST, df$g)

i.e. you want the first 2 columns of df; you want the names before ., and you split the data frame. Reorganize your tasks and you will have a much clearer view of the problem.

BTW, <<- is not necessarily a horrible animal; you can use it very safely by creating the variable name in the top environment, e.g.

x <- 0
f <- function() x <<- 1

The danger only exists if you do not create the variable name at all in any places, so R has to go all the way up to the global environment, and that is usually a very bad practice.