Section 1.1: New Inline Chunk Options

Most users are familiar with chunk options in R Markdown. By specifying options when creating a code chunk, you can control how the output is displayed. For instance, the following code:

# some R code

will show the results without revealing the underlying code. Conversely, this snippet:

# some python code

will display the code without executing it. While there are many options available, they can become cumbersome when written in curly braces. However, with knitr version 1.35+, you can now specify chunk options line by line using a new special comment format, such as:

#| echo = FALSE, out.width = "80%"

#| fig.cap = "My caption"

my_plot

Section 1.2: Conditional Evaluation of Code Chunks

Did you know that you can incorporate conditions into your chunk options? This feature allows you to execute a chunk based on specific criteria. For example, this chunk will run only if the dataset my_data contains more than three rows:

#| eval = nrow(my_data) > 3

my_data

Additionally, you can create chunks that adjust their output based on whether you're rendering to PDF or HTML, thereby maintaining a single Rmd file for different outputs. For example:

#| eval = knitr::is_html_output()

# code for HTML output (e.g., interactive graphic)

#| eval = knitr::is_latex_output()

# code for PDF output (e.g., static graphic)

Alternatively, you can use if statements with these knitr functions as follows:

if (knitr::is_html_output()) {

# code for HTML output

} else {

# code for LaTeX output

}

Section 1.3: Direct JavaScript Integration for Shiny Apps

While many developers structure their Shiny applications using separate ui.R and server.R files, you can also develop a complete app within a single R Markdown file. This approach allows for easy customization with JavaScript, which can be included directly in a JS chunk. For instance, if you want to limit the character count in a textarea input box, the standard Shiny UI function:

shiny::textAreaInput(

"comment",

"Enter your comment:"

)

creates a textarea without built-in character limits. However, with a bit of JavaScript/jQuery, you can easily add a maxlength attribute as shown below:

$('[id="comment"]').attr('maxlength', 1000)

Section 2.1: Modularizing Your Code with Chunk Options

As your document or application grows in length and complexity, managing the code within chunks can become tedious. A more efficient approach is to extract the code into separate R files and reference them in your chunks. For example:

#| code = readLines("my_setup_code.py")

# python code for setup

Section 2.2: Enhancing Document Style with CSS Chunks

To personalize the appearance of your document or application, you can utilize CSS code chunks for easy styling. After rendering the document and inspecting it in Google Chrome to identify the specific elements you wish to modify, you can insert a CSS chunk. For example, to change the background color of your document to a light blue, simply add:

body {

background-color: #d0e3f1;

}

I hope you find these handy tricks valuable! If you have any additional tips to share, please feel free to leave a comment.

Originally, I specialized in Pure Mathematics before transitioning into Psychometrics and Data Science. I am passionate about applying the precision of these fields to complex human issues. Additionally, I enjoy coding and have a strong affinity for Japanese RPGs. Connect with me on LinkedIn or Twitter, and check out my blog at drkeithmcnulty.com.

In the first video, "R Markdown Advanced Tips to Become a Better Data Scientist & RStudio Connect," Tom Mock shares advanced tips that can elevate your data science skills.

The second video, "R Markdown Tips," presents essential tips that can enhance your efficiency and effectiveness when using R Markdown.