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}

many people think <<>>= has to be ended by @ but that is not true; the original syntax of literate programming defined <<>>= to open code chunks, and @ to open documentation chunks, so I can use two <<>>= successively and they are two separate chunks; you can certain add @ before the second chunk, but that is unnecessary because there is no text between the two chunks

knitr does not produce Rplots.pdf at all (details at yihui/knitr#9)

Thanks, I didn't know that. Regarding Rplots.pdf, it is definitely created when I knit the gist above. Do you mean that it's not knitr's fault that it exists (which is correct, grid opens a device also in interactive use to test the fontsize)?

I see. I did not know convertWidth() has to open a device. I'll fix this. Thanks!

fixed; will appear in my next commit

Thanks!

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)
```