code.R

library(dplyr)

a <- data.frame(foo = 1:10, bar = "bar")
b <- tbl_df(a)

a[,1]
b[,1]

paste0(a[,1], "!")
paste0(b[,1], "!")

output.txt

> library(dplyr)
> 
> a <- data.frame(foo = 1:10, bar = "bar")
> b <- tbl_df(a)
> 
> a[,1]
 [1]  1  2  3  4  5  6  7  8  9 10
> b[,1]
Source: local data frame [10 x 1]

   foo
1    1
2    2
3    3
4    4
5    5
6    6
7    7
8    8
9    9
10  10
> 
> paste0(a[,1], "!")
 [1] "1!"  "2!"  "3!"  "4!"  "5!"  "6!"  "7!"  "8!"  "9!"  "10!"
> paste0(b[,1], "!")
[1] "1:10!"