Format Numeric Columns with Specified Digits

Source: R/format_digits.R

The format_digits function formats numeric columns in a data frame or data table by rounding numbers to a specified number of decimal places and converting them to character strings. It can optionally format the numbers as percentages.

format_digits(data, cols = NULL, digits = 2, percentage = FALSE)

Arguments

data

A data.frame or data.table. The input data containing numeric columns to format.

cols

An optional numeric or character vector specifying the columns to format. If NULL (default), all numeric columns are formatted.

digits

A non-negative integer specifying the number of decimal places to use. Defaults to 2.

percentage

A logical value indicating whether to format the numbers as percentages. If TRUE, the numbers are multiplied by 100 and a percent sign (%) is appended. Defaults to FALSE.

Value

A data.table with the specified numeric columns formatted as character strings with the specified number of decimal places. If percentage = TRUE, the numbers are shown as percentages.

Details

The function performs the following steps:

  1. Validates the input parameters, ensuring that data is a data.frame or data.table, cols (if provided) are valid column names or indices, and digits is a non-negative integer.

  2. Converts data to a data.table if it is not already one.

  3. Creates a formatting function based on the digits and percentage parameters:

    • If percentage = FALSE, numbers are rounded to digits decimal places.

    • If percentage = TRUE, numbers are multiplied by 100, rounded to digits decimal places, and a percent sign (%) is appended.

  4. Applies the formatting function to the specified columns:

    • If cols is NULL, the function formats all numeric columns in data.

    • If cols is specified, only those columns are formatted.

  5. Returns a new data.table with the formatted columns.

Note

  • The input data must be a data.frame or data.table.

  • If cols is specified, it must be a vector of valid column names or indices present in data.

  • The digits parameter must be a single non-negative integer.

  • The original data is not modified; a modified copy is returned.

Examples

# Example: Number formatting demonstrations

# Setup test data
dt <- data.table::data.table(
  a = c(0.1234, 0.5678),      # Numeric column 1
  b = c(0.2345, 0.6789),      # Numeric column 2
  c = c("text1", "text2")     # Text column
)

# Example 1: Format all numeric columns
format_digits(
  dt,                         # Input data table
  digits = 2                  # Round to 2 decimal places
)
#>         a      b      c
#>    <char> <char> <char>
#> 1:   0.12   0.23  text1
#> 2:   0.57   0.68  text2

# Example 2: Format specific column as percentage
format_digits(
  dt,                         # Input data table
  cols = c("a"),              # Only format column 'a'
  digits = 2,                 # Round to 2 decimal places
  percentage = TRUE           # Convert to percentage
)
#>         a      b      c
#>    <char>  <num> <char>
#> 1: 12.34% 0.2345  text1
#> 2: 56.78% 0.6789  text2