如何使用字符变量来引用 R 中的 data.frame？

Question

I have a dynamic number of data.frames depending on input - n_tables.

n_tables = 5 ## This may vary between 3 to 12
for(i in 1:n_tables){
    assign(paste0("r", i),data.frame(X = c("a","b","c"),Y = runif(3,0,10)))
}

Now, I need to put all these data.frames in a list and subset them. I have tried the below code but not working -

t <- paste0("r",1:n_tables)
p <-lapply(t,function(x){(x[x$X == "a",])})

Thank you in advance.

Answer 1

You can use get() to fetch the object, ie,

p <-lapply(t,function(x){x <- get(x);x[x$X == "a",]})

such that

> p
[[1]]
  X        Y
1 a 5.550481

[[2]]
  X        Y
1 a 5.365116

[[3]]
  X        Y
1 a 5.783017

[[4]]
  X        Y
1 a 2.782952

[[5]]
  X        Y
1 a 2.123357

Answer 2

We get the objects into a list with mget , loop over the list with map and filter the rows from the column 'X'

library(purrr)
library(dplyr)
map(mget(t), ~ .x %>% 
                   filter(X == "a"))