Rownames as column in list of dataframes

Question

I'd like to create a column year for each dataframe in a list based on its rownames. This question has been asked before on SO but unfortunately the answer doesn't help. So, is there a way to do it?

mylist <- list(structure(list(a = 1:10), .Names = "a", row.names = 1991:2000, class = "data.frame"), 
            structure(list(a = 1:10), .Names = "a", row.names = 1992:2001, class = "data.frame"))

Expected outcome:

[[1]]
      a year
1991  1 1991
1992  2 1992
1993  3 1993
1994  4 1994
1995  5 1995
1996  6 1996
1997  7 1997
1998  8 1998
1999  9 1999
2000 10 2000

[[2]]
      a year
1992  1 1992
1993  2 1993
1994  3 1994
1995  4 1995
1996  5 1996
1997  6 1997
1998  7 1998
1999  8 1999
2000  9 2000
2001 10 2001

Answer 1

We can use Map

Map(cbind, mylist, year= lapply(mylist, rownames))

Answer 2

Here's another option:

lapply(mylist, function(df) transform(df, year = rownames(df)))

Just for fun, you could also use dplyr's add_rownames function:

lapply(mylist, dplyr::add_rownames, 'year')