In general, the sum of rounded numbers (e.g., using the base::round function) is not the same as their rounded sum. This solution applies the following algorithm

1. Round down to the specified number of decimal places

2. Order numbers by their remainder values

3. Increment the specified decimal place of values with ‘k’ largest remainders, where ‘k’ is the number of values that must be incremented to preserve their rounded sum

round_preserve_sum(x, digits = 0)

Arguments

x

vector to sum

digits

number of decimals for rounding

Examples

sum(c(0.333, 0.333, 0.334))
#> [1] 1
round(c(0.333, 0.333, 0.334), 2)
#> [1] 0.33 0.33 0.33
sum(round(c(0.333, 0.333, 0.334), 2))
#> [1] 0.99
round_preserve_sum(c(0.333, 0.333, 0.334), 2)
#> [1] 0.33 0.33 0.34
sum(round_preserve_sum(c(0.333, 0.333, 0.334), 2))
#> [1] 1