draw a table by gridExtra in knitr

grid-table.Rnw

\documentclass{article}

\begin{document}

We can draw a table with the gridExtra package, and one problem is to
pre-determine the size of the table plot to remove the extra white
margin. Below is an example that shows you how to do it (courtesy of
baptiste auguie).

<<setup>>=
library(gridExtra)
g = tableGrob(head(iris, 4))
<<draw-table, dev='png', dpi=150, fig.width=convertWidth(grobWidth(g), "in", value=TRUE), fig.height=convertHeight(grobHeight(g), "in", value=TRUE)>>=
grid.draw(g)
@

\end{document}

Was looking for exactly this! Is there any way to reduce the amount of typing involved? I'm using your code in a similar way with Rmd:

```{r} 
g = tableGrob(head(iris, 4))
```{r draw-table, dev='png', dpi=72, fig.width=convertWidth(grobWidth(g), "in", value=TRUE), fig.height=convertHeight(grobHeight(g), "in", value=TRUE)}
grid.draw(g)
```