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Exactly rounded mean

Source: R/mean.R
xsum_mean.Rd

xsum_mean() divides the exact sum by the number of terms and rounds once: the result is the correctly rounded value of the true mean, not xsum(x) / length(x), which would round twice. Base mean() makes a second pass to correct its first estimate, but its accumulator is still platform-dependent.

Usage

xsum_mean(x, na.rm = FALSE)

Arguments

x

A numeric, integer, logical or complex vector.

na.rm

Remove NA and NaN values before summing?

Value

A double of length one (complex for complex x).

Details

Special values follow the table in xsum(). The mean of no values is NaN, as in base R. xsum divides by a 32-bit count, so a mean over more than 2^32 - 1 terms signals a zuexact_count_error.

See also

Other means: xsum_weighted_mean()

Examples

# Base mean() is accurate to three digits here (Neal, 2015).
x <- c(1e15, -1e15, 0.1)
mean(x)
#> [1] 0.03333876
xsum_mean(x)
#> [1] 0.03333333