R Syntax Basics

A few rules cover most of what R code looks like.

One expression per line. No semicolons are needed.

Curly braces group code, and conditions go in parentheses:

if (10 > 5) {
  cat("Ten is bigger\n")
}

Ten is bigger

Indentation is two spaces by convention (RStudio applies it with Ctrl + I). R doesn't require it, but it keeps code readable.

Comments start with #.

Case matters. Total and total are different names.

Names can contain letters, numbers, dots, and underscores, but can't start with a number. The tidyverse style guide recommends snake_case: total_price, mean_height.

Function calls use parentheses, and arguments can be named:

round(3.14159, digits = 2)
round(3.14159, 2)

[1] 3.14
[1] 3.14

Naming arguments makes code clearer, especially for less common ones.

Common mistakes

• Unfinished expressions. If a line ends with an operator like + or an open parenthesis, R continues onto the next line — handy, but a missing ) leaves the console waiting with a + prompt.
• Putting else on a new line at the top level of a script. Keep it on the same line as the closing brace: } else {.