Subsetting from an object created from a character string by the get() function

Question

This is an example from the help page of the assign function:

> a <- 1:4
> assign("a[1]", 2)
> a[1] == 2          # FALSE
> get("a[1]") == 2   # TRUE

Instead of creating a whole new object a[1] , I wish I could overwrite the 1st member of the object a . I tried this:

> get("a")[1] <- 2
Error in get("a")[1] <- 2 : 
  target of assignment expands to non-language object

But it didn't work. I wish get() <- were a valid expression, but it's not. Is there any alternative for this?

What I'm trying to do is:

I have a lot of objects (data frames): x11 x12 x13 x21 x22 x23 x31 ... (almost 20 of them). All of these objects contain 30 years of daily data. They were created using:

> for(i in c("x11", "x12", "x13", ...)) {
>   assign(i, read.csv())}

And now, I'm attempting to work with my data using a code like this:

> for(i in c("x11", "x12", "x13", ...)) {
>   for(j in 1:n) {
>     get(i)[j] <- "some.input"}}

And it gives me this message:

Error in get("x11")[] <- "some.input" : 
  target of assignment expands to non-language object

I hope, the problem I'm facing is understandable.

Answer 1

Agree with David's comments above, you can probably do this with a list of data frames. Your creation code would look like:

df_list <- lapply(c("x11", "x12", "x13", ...), function(i) {
   read.csv(...)
})

and your modification code:

for(i in 1:length(df_list)) {
   for(j in 1:n) {
        df.list[[i]][j] <- "some.input"}}