Different ways to set figure size in RMarkdown

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Markdown is thought as a “lightweight” markup language, hence the name markdown. That’s why formatting options are scarce. However, there are some extensions, for instance brought by RMarkdown.

One point of particular interest is the sizing of figures. Let’s look at some ways how to size a figure with RMarkdown.

We take some data first:

data(mtcars) 
names(mtcars) 
##  [1] "mpg"  "cyl"  "disp" "hp"   "drat" "wt"   "qsec" "vs"   "am"   "gear"
## [11] "carb"

Not let’s plot.

Define size in YAML header

We can define the size of figures globally in the YAML part, like this for example.

--- 
title: "My Document" 
output: html_document: 
fig_width: 6 
fig_height: 4 
--- 

Defining figures size for R plots

Define figure size as global chunk option

As a first R-chunk in your RMD document, define the general chunk settings like this:

knitr::opts_chunk$set(fig.width=12, fig.height=8) 

Chunk options

We can set the chunk options for each chunk too. With figh.height and fig.width we can define the size. Note that the numbers default to inches as unit: {r fig1, fig.height = 3, fig.width = 5}.

plot(pressure) 

plot of chunk fig1

For a plot of different size, change simple the numbers: {r fig2, fig.height = 3, fig.width = 3, fig.align = "center"}.

plot(pressure) 

plot of chunk fig2

Alternatively, you may change the aspect ratio of the image: {r fig3, fig.width = 5, fig.asp = .62}.

plot(pressure) 

plot of chunk fig3

Note that the aspect ratio is based on the fig.width specified by you. See here.

Different options for different output formats

The options for figure sizing also depend on the output format (HTML vs. Latex, we do not mention Word here). For instance, in Latex percentage is allowed, as is specified on the options page: {r fig4, out.width = '40%'}.

plot(pressure) 

plot of chunk fig4

But note that it appears to work in HTML too.

Differnce between figure size and output size

We are allowed to specify the figure size, and secondly the size of the figure as to appear in the output. For example, if you set the size of a ggplot figure to large, then fonts etc. will appear tiny. Better do not scale up fig.height, but set out.width accordingly, eg., like this out.width = "70%".

Using Pandoc’s Markdown for figure sizing

Alternatively, instead of using R for plotting, you can just load an image. Of course, it is possible to just use markdown for that: ![](path/to/figure/figure.png).

Change the figure size like this: ![](file.jpg){ width=50% }. Note that no space are allowed around the = (equal sign), and the curly brace { needs to come right after the ) brace; no space allowed.

Similarly, with path to local folder:

![](../../sebastiansauer.github.io/images/2016-10-17/unnamed-chunk-5-1.png.png)

{ width=20% }

Centering is not really part of markdown. But there are some workarounds. See:

![](https://sebastiansauer.github.io/images/2016-10-17/unnamed-chunk-5-1.png){ width=20% }

I used this code:

<center>
![](https://sebastiansauer.github.io/images/2016-10-17/unnamed-chunk-5-1.png){
width=20% }
</center>

Using the knitr function include_graphics

We can use the knitr function include_graphics which is convenient, as it takes care for the different output formats and provides some more features (see here the help file).

plot of chunk fig5

Note that online sources are allowed. Don`t forget to load knitr previously.

plot of chunk }{r fig6

If all fails

Just resize the image with your favorite photo/image manager such as Gimp, Photoshop, Preview App etc.

Further reading Finde good advice on Yihui’s option page

here. The Book “R for Data Science” by Hadley Wickham and Garrett Grolemund (read here) is a great resource too. Read chapter 28 on diagrams here. Pandoc’s user guide has some helpful comments on figures sizing with Pandoc’s markdown .

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