取消列出数据框列表并在循环中分配名称 - R

Question

I need to unlist several lists of dataframes whilst conserving and adapting their names.

Each dataframe needs to be labelled with the respective date.

As in

`Data_2021-05-07`$df1
`Data_2021-05-08`$df1
`Data_2021-05-09`$df1
 ...
`Data_2021-05-29`$df1
`Data_2021-05-30`$df1
`Data_2021-05-31`$df1

Here's what I got

May <- c("07", "08", "09", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30", "31")


for (i in May){

Date <- paste("2021-05", i, sep = "-")
List <- noquote(paste("`Data_", Date, "`", sep = ""))
File <- parse(noquote(paste(List, "$df1", sep = "")))
DfName <- paste("df1", Date, sep = "_")

assign(DfName, File)

}

When I run that code I get the following code I get this error:

cannot open file '`Data_2021-05-07`$df1': No such file or directoryError in file(filename, "r") : cannot open the connection

I know the error stems from

File <- parse(noquote(paste(List, "$df1", sep = "")))

However, not only can I see it in my global environment, when I run:

`Data_2021-05-07`$df1

I get the intended result.

Would appreciate any insight into what is wrong with my code.

Answer 1

We can use get to get the value of the data

for (i in May){

   Date <- paste("2021-05", i, sep = "-")
   List <-  paste0("Data_", Date)
   File <- get(List)[["df1"]]
   DfName <- paste("df1", Date, sep = "_")

    assign(DfName, File)
}

---

Another option is to use mget to return all objects in a list , loop over the list with lapply , extract the 'df1' (it is recommended to keep it in a list instead of creating multiple objects), but if we need objects, use list2env

lst1 <- lapply(mget(paste0("Data_2021-05-", May)), `[[`, "df1")
names(lst1) <- paste0("df1", names(lst1))
list2env(lst1, .GlobalEnv)