signifz: Round values to specified number of significant digits

In leeper/UNF: Tools for Creating Universal Numeric Fingerprints for Data

Round values to specified number of significant digits

Description

Rounds the value to a specified number of significant digits, using IEEE 754 rounding towards zero rounding mode.

Usage

signifz(x, digits = 6)

Arguments

x	A numeric vector.
digits	An integer indicating the precision to be used.

Details

This function rounds the values in its first argument to the specified number of significant digits, using IEC 60559/IEEE 754 “round towards zero” mode. This is an alternative to the round function, which rounds toward nearest, ties to even. This is designed to be used internally by unf3 and unf4 (though the original implementations do not seem to actually use the function). unf5 uses round instead. Rounding toward zero assures that signifz(signifz(x,digits=m),digits=n) = signifz(x,digits=n) for $m>n$, an important property for creating approximate fingerprints. It can, however, produce more rounding error than rounding toward nearest. The maximum log relative error (LRE) for the former is (digits-1) while the maximum LRE for the latter is ‘digits’. Hence, you may wish to use one more significant digit with signifz than with signif.

Author(s)

Micah Altman

See Also

signif, unf

Examples

# note the difference
signif(pi,digits=5)
signifz(pi,digits=5)

leeper/UNF documentation built on April 20, 2022, 6:32 p.m.