format()

format(x, trim = FALSE, digits = NULL, nsmall = 0, scientific = NA, ...)

The format() function formats R objects for pretty printing. It converts objects to character vectors with controlled formatting.

Syntax

format(x, trim = FALSE, digits = NULL, nsmall = 0, scientific = NA, 
       big.mark = "", big.interval = 3, small.mark = "", 
       small.interval = 5, decimal.mark = ".", ...)

Parameters

Parameter	Type	Default	Description
x	object	required	An atomic object to format
trim	logical	FALSE	If TRUE, removes leading whitespace
digits	integer	NULL	Number of significant digits
nsmall	integer	0	Minimum decimal places
scientific	logical	NA	Force/disable scientific notation
big.mark	character	""	Separator for thousands
decimal.mark	character	”.”	Decimal separator
...	arguments	passed to format.info()

Examples

Basic number formatting

# Default formatting pads with spaces
format(123.456)
# [1] "123.456"

# Fix decimal places
format(123.456, nsmall = 2)
# [1] "123.46"

Controlling decimal places

# Minimum decimal places
format(c(1, 2.5, 3.14159), nsmall = 2)
# [1] "1.00"    "2.50"    "3.14"

# Significant digits
format(pi, digits = 5)
# [1] "3.1416"

Adding thousand separators

# Add commas as thousand separators
format(1234567, big.mark = ",")
# [1] "1,234,567"

format(1234567.89, big.mark = ",", nsmall = 2)
# [1] "1,234,567.89"

Trimming whitespace

# Default adds padding for alignment
format(1:5)
# [1] "1" "2" "3" "4" "5"

# Trim to remove padding
format(1:5, trim = TRUE)
# [1] "1" "2" "3" "4" "5"

Common Patterns

Pretty-printing tables

# Create aligned numeric output
df <- data.frame(
  name = c("Sales", "Profit", "Growth"),
  value = c(1234567, 98765, 0.12345)
)

df$value <- format(df$value, big.mark = ",", nsmall = 2)
print(df)
#    name        value
# 1  Sales 1,234,567.00
# 2 Profit     98,765.00
# 3 Growth          0.12

Combining with paste

# Create formatted output strings
x <- 1234.5678
paste0("The value is: ", format(x, nsmall = 2))
# [1] "The value is: 1234.57"

# Currency formatting
amount <- 1999.99
paste0("$", format(amount, big.mark = ",", nsmall = 2))
# [1] "$1,999.99"

See Also

• stringr::formatC
• base::sprintf