r - Control alignment of two side-by-side plots in knitr

Question

I cannot figure out how to arrange two side-by-side plots as explained in the knitr graphics manual page 2 (http://yihui.name/knitr/demo/graphics/). I use the following MWE and the output is below. I would like them to be aligned as shown in the manual for the two cars plots (also on page 2 of the manual). The pdf is generated in RStudio (Knit to PDF).

---
title: "Untitled"
output: pdf_document
---

## R Markdown

```{r,echo=FALSE,out.width='.49\linewidth', fig.width=3, fig.height=3}

barplot(1:4)
barplot(4:7)

```

Answer 1

To center two plots you can add fig.align='center'to your chunk options. If it produces one plot above the other add also fig.show='hold'. The result should be two centered graphs.

So your final chunk option should look something like:

{r,echo=FALSE, out.width='.49\linewidth', fig.width=3, fig.height=3,fig.show='hold',fig.align='center'}