Use object names within a list in lapply/ldply

Question

In attempting to answer a question earlier, I ran into a problem that seemed like it should be simple, but I couldn\'t figure out.

If I have a list of dataframes:

Answer 1

Define your list with names and it should give you an .id column with the data.frame name

df.list <- list(df1=df1, df2=df2, df3=df3)
df.all <- ldply(df.list, rbind)

Output:

  .id a           x
1 df1 1  1.84658809
2 df1 2 -0.01177462
3 df1 3  0.58579469
4 df2 1 -0.64748756
5 df2 2  0.24384614
6 df2 3  0.59012676
7 df3 1 -0.63037679
8 df3 2 -1.17416295
9 df3 3  1.09349618

Then you can know the data.frame name from the column df.all$.id

Edit: As per @Gary Weissman's comment if you want to generate the names automatically you can do

names(df.list) <- paste0('df',seq_along(df.list)