Formatting

API Reference

Number Formatting

# d3.format(specifier)

Returns a new format function with the given string specifier. A format function takes a number as the only argument, and returns a string representing the formatted number. The format specifier is modeled after Python 3.1's built-in format specification mini-language. The general form of a specifier is [sign][0][width][,][.precision][type]. The sign can be one of the following:

• plus ("+") - a sign should be used for both positive and negative numbers.
• minus ("-") - a sign should be used only for negative numbers. (This is the default.)
• space (" ") - a leading space should be used on positive numbers, and a minus sign on negative numbers.

The comma (",") option enables the use of a comma for a thousands separator. The width defines the minimum field width. If not specified, then the width will be determined by the content. If width is preceded by a zero ("0"), zero-padding is enabled. The available type values are:

• exponent ("e") - use Number.toExponential.
• general ("g") - use Number.toPrecision.
• fixed ("f") - use Number.toFixed.
• integer ("d") - use Number.toString, but ignore any non-integer values.
• rounded ("r") - like fixed, but round to precision significant digits.
• percentage ("%") - like fixed, but multiply by 100 and suffix with "%".
• rounded percentage ("p") - like rounded, but multiply by 100 and suffix with "%".

The type "n" is also supported as shorthand for ",g". The precision indicates how many digits should be displayed after the decimal point for a value formatted with types "f" and "%", or before and after the decimal point for a value formatted with types "g", "r" and "p".

Date Formatting

See the d3.time module.