Combining data frames in R

Question

I have several data frames with the same columns and I would like to combine them in such a way that identifies which data frame they are from. For example, if in data frame #1, I have this data:

  x y
1 a 1
2 b 4

And in data frame #2, I have this data:

  x y
1 d 6
2 e 7

I would like to combine them into one data frame with a new column that identifies which data frame they came from:

  frame x y
1     1 a 1
2     1 b 4
3     2 d 6
4     2 e 7

The frame column identifies that rows 1 and 2 are from data frame #1, and rows 3 and 4 are from data frame #2. I'm using strings to identify my data frames, but I just used numbers here to make the example simpler.

Answer 1

Using the same list approach as @Shambho with do.call:

dfList <- list(
    df1 = data.frame(x=letters[1:2],y=1:2),
    df2 = data.frame(x=letters[3:4],y=3:4)
)


data.frame(
    frame = rep(seq_along(dfList), sapply(dfList, nrow)),
    do.call(rbind, dfList), row.names=NULL
)

##   frame x y
## 1     1 a 1
## 2     1 b 2
## 3     2 c 3
## 4     2 d 4

Answer 2

Or like this?:

Assuming df1 and df2 are your data frame 1 and 2, respectively:

data.frame(frame=rep(1:2,lapply(list(df1,df2),function(x) dim(x)[1])),rbind(df1,df2))