bind many data frames adding a column with their id [duplicate]

Question

I have many data frames named repeatably:

df.1 <- data.frame("x"=c(1,2), "y"=2)
df.2 <- data.frame("x"=c(2,4), "y"=4)
df.3 <- data.frame("x"=2, "y"=c(4,5))

All data frames have the same number of rows and columns. I want to bind them, adding a column with the id of the data frame. The id would be the name of the source data frame.

I know I could do this manually:

rbind(data.frame(id = "df.1", df.1),
      data.frame(id = "df.2", df.2),
      data.frame(id = "df.3", df.3))

But there's a lot of them and their number will change in the future.

I tried writing for loops but they didn't work. I suppose that's because I'm basing them on a list of strings containing data frames' names rather than a list of data frames themselves.

df_names <- ls(pattern = "df.\\d+")

for (i in df_names) {
  i$id <- i
  i
}

...but I also haven't found any automated way of creating a list of data frames with repeatable names. And even if I do, I'm not that sure the for-loop above would work :)

Answer 1

You could use parse and eval to get the data frames from df_names:

do.call(rbind, lapply(df_names, function(x){data.frame(id=x, eval(parse(text=x)))}))


    id x y
1 df.1 1 2
2 df.1 2 2
3 df.2 2 4
4 df.2 4 4
5 df.3 2 4
6 df.3 2 5

Answer 2

There is also combine from the "gdata" package:

library(gdata)
combine(df.1, df.2, df.3)
#   x y source
# 1 1 2   df.1
# 2 2 2   df.1
# 3 2 4   df.2
# 4 4 4   df.2
# 5 2 4   df.3
# 6 2 5   df.3

Answer 3

Another approach using mget:

dat <- do.call(rbind, mget(df_names))
dat$id <- sub("\\.\\d+$", "", rownames(dat))

#        x y   id
# df.1.1 1 2 df.1
# df.1.2 2 2 df.1
# df.2.1 2 4 df.2
# df.2.2 4 4 df.2
# df.3.1 2 4 df.3
# df.3.2 2 5 df.3