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Round a decimal to the precise decimal value of a specified fractional denominator. Common use cases include addressing floating point imprecision and enforcing that data values fall into a certain set.

E.g., if a decimal represents hours and values should be logged to the nearest minute, round_to_fraction(x, 60) would enforce that distribution and 0.57 would be rounded to 0.566667, the equivalent of 34/60. 0.56 would also be rounded to 34/60.

Set denominator = 1 to round to whole numbers.

The digits argument allows for rounding of the subsequent result.


round_to_fraction(x, denominator, digits = Inf)



A numeric vector


The denominator of the fraction for rounding (a scalar or vector positive integer).


Integer indicating the number of decimal places to be used after rounding to the fraction. This is passed to base::round()). Negative values are allowed (see Details). (Inf indicates no subsequent rounding)


the input x rounded to a decimal value that has an integer numerator relative to denominator (possibly subsequently rounded to a number of decimal digits).


If digits is Inf, x is rounded to the fraction and then kept at full precision. If digits is "auto", the number of digits is automatically selected as ceiling(log10(denominator)) + 1.


round_to_fraction(1.6, denominator = 2)
#> [1] 1.5
round_to_fraction(pi, denominator = 7) # 22/7
#> [1] 3.142857
round_to_fraction(c(8.1, 9.2), denominator = c(7, 8))
#> [1] 8.142857 9.250000
round_to_fraction(c(8.1, 9.2), denominator = c(7, 8), digits = 3)
#> [1] 8.143 9.250
round_to_fraction(c(8.1, 9.2, 10.3), denominator = c(7, 8, 1001), digits = "auto")
#> [1]  8.1400  9.2500 10.2997