Customizing Plot Size in R Markdown

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R Markdown is a powerful tool for creating dynamic reports and documents that combine code, output, and commentary. One important aspect of creating appealing and readable reports is properly sizing plots. In this article, we’ll explore how to customize plot sizes in R Markdown.

Understanding R Markdown

R Markdown is a file format that allows you to create fully reproducible documents that combine narrative, code, and results. By using R Markdown, you can weave together your R code and documentation, producing reports in various formats, including HTML, PDF, and Word.

Importance of Plot Size

When generating plots in R Markdown, the size of the plots can greatly affect the readability and professionalism of your reports. A plot that is too small might not convey the necessary details, while a plot that is too large can overwhelm the document layout.

Setting Plot Size in R Markdown

There are several ways to customize plot sizes in R Markdown. Here’s a breakdown of the primary methods:

1. Chunk Options:

   The most straightforward way to control the size of plots is using chunk options. You can specify fig.width and fig.height within the code chunk that generates the plot. Here’s an example:

   ```{r, fig.width=6, fig.height=4}
   plot(cars)
   

   In this example, the plot will have a width of 6 inches and a height of 4 inches.
   

2. Global Settings:

   If you prefer to set a default plot size for all plots in your document, you can include global chunk options at the beginning of your R Markdown file. This way, you don't have to specify the size in each chunk:

   ```{r setup, include=FALSE}
   knitr::opts_chunk$set(fig.width=7, fig.height=5)
   

3. Using dev.new Function:

   Another way to set the plot size is by using the dev.new function, which opens a new graphics device. This is less common but can be useful in certain scenarios:

   dev.new(width=6, height=4)
   plot(cars)
   

   Note that this approach is more commonly used in interactive sessions rather than R Markdown documents.

4. Custom Plot Functions:

   You can also create custom functions to generate plots with specific sizes. For instance:

   create_custom_plot <- function(width, height) {
     par(mfrow=c(1, 1), mar=c(4, 4, 2, 1), 
         pin=c(width, height))
     plot(cars)
   }
   
   ```{r}
   create_custom_plot(6, 4)
   

Adjusting Plot Aspect Ratios

Sometimes, it’s not just the size but the aspect ratio that matters. You can control the aspect ratio by carefully choosing the width and height. For example, if you want a square plot, you might use: