Align two data.frames next to each other with knitr?

Question

I\'m new to knitr (and also quite new to R), so this might be a dumb question...

I have two data.frames, which both have two columns, but different numbers of rows.

Answer 1

The development version of knitr (on Github; follow installation instructions there) has a kable() function, which can return the tables as character vectors. You can collect two tables and arrange them in the two cells of a parent table. Here is a simple example:

```{r two-tables, results='asis'}
library(knitr)
t1 = kable(mtcars, format='html', output = FALSE)
t2 = kable(iris, format='html', output = FALSE)
cat(c('<table><tr valign="top"><td>', t1, '</td><td>', t2, '</td><tr></table>'),
    sep = '')
```

You can also use CSS tricks like style="float: [left|right]" to float the tables to the left/right.

If you want to set cell padding and spacing, you can use the table attributes cellpadding / cellspacing as usual, e.g.

```{r two-tables, results='asis'}
library(knitr)
t1 = kable(mtcars, format='html', table.attr='cellpadding="3"', output = FALSE)
t2 = kable(iris, format='html', table.attr='cellpadding="3"', output = FALSE)
cat(c('<table><tr valign="top"><td>', t1, '</td>', '<td>', t2, '</td></tr></table>'),
    sep = '')
```

See the RPubs post for the above code in action.

Answer 2

Would you settle for "an image" of data.frames? Clearly my solution is crude, feel free to fiddle with the details (spacing between data.frames, for example).

Two data.frames, side by side
========================================================

```{r}
library(gridExtra)
x <- data.frame(a = runif(5), b = runif(5))
y <- data.frame(a = runif(7), b = runif(7))

grid.arrange(tableGrob(x), tableGrob(y), ncol = 2)
```