Syntax

Object names

• Variable and function names should use only letters, numbers, and underscores (_) and not include dots (mainly to avoid confusion with base R function names). CamelCases are also fine.

#Good
school_type
SchoolType

#Bad
school.type

• Variable names should be as concise and meaningful as possible:

#Good
day_one

#Bad
first_day_of_the_month
d1mth

Spacing

Make code easier to read, place a space:

• After a comma.

x[, 1]

• After function arguments.

# Good
function(x) {}

# Bad
function (x) {}
function(x){}

• Inside embracing operators { }

group_by({{ by }}) %>%
summarise(maximum = max({{ var }}, na.rm = TRUE))

• Surrounding infix operators (=, +, -, <-, etc.)

mean(x, na.rm = TRUE)

Function calls

• Omit names of data arguments, because they are used so frequently.

# Good
mean(1:10, na.rm = TRUE)

# Bad
mean(x = 1:10, , FALSE)
mean(, TRUE, x = c(1:10, NA))

• Avoid assignment:

# Good
x <- complicated_function()
if (nzchar(x) < 1) {
  # do something
}

# Bad
if (nzchar(x <- complicated_function()) < 1) {
  # do something
}

Control flow

• Curly brackets { } determine the hierarchy of your code. Make it clear.

  • { should be the last character on the line. Place in the line below (indented) the code to be ran.

  • The contents should be indented by two spaces.

  • } should be the first character on the line. If it is the closing bracket, place it in a separate line with no indentation.

if (y == 0) {
  if (x > 0) {
    log(x)
  } else {
    message("x is negative or zero")
  }
} else {
  y^x
}

Warning

Note that, if an if statement is used, else should be on the same line as }. Moreover, if the statement is very simple, it might make more sense to just write it out all in one line.

temperature <- if (x > 20) "nice" else "cold"

Functions

Naming functions

Tip

Try using verbs to name functions. Instead, try using nouns for variables.

# Good
add_row()
permute()

# Bad
row_adder()
permutation()

Explicit returns

Be clear about your intent to return() an object instead of relying on R’s internal implicit return function.

# Good
AddValues <- function(x, y) {
return(x + y)
}

# Bad
AddValues <- function(x, y) {
x + y
}

Tip

Avoid using attach() as it increases dramatically the chances of creating errors.

Further material

In general, we follow Google’s R Style Guide, which is based (and thus, so are we) on the Tidyverse Style Guide.

Warning

Exceptions to Google’s R Style Guide:

• We do not follow their naming conventions:

  • Do not use dots
  • Underscores or camel-case are fine.

• See our conventions for line length

• We do not require that all functions have a comment block describing their uses. We encourage to do so when the purpose of a function would not be clear or whenever the function will be used outside of the file in which it is defined.