The machine epsilon is the difference between 1.0 and the next number that can be represented by the machine. By default, this function uses epsilon * 1000 as the tolerance. First it scales the values so that they have a mean of 1, and then it checks if the difference between them is larger than the tolerance.

zero_range(x, tol = 1000 * .Machine$double.eps) ## Arguments x numeric range: vector of length 2 tol A value specifying the tolerance. ## Value logical TRUE if the relative difference of the endpoints of the range are not distinguishable from 0. ## Examples eps <- .Machine$double.eps
zero_range(c(1, 1 + eps))
#>  TRUE
zero_range(c(1, 1 + 99 * eps))
#>  TRUE
zero_range(c(1, 1 + 1001 * eps))
#>  FALSE
zero_range(c(1, 1 + 2 * eps), tol = eps)
#>  FALSE

# Scaling up or down all the values has no effect since the values
# are rescaled to 1 before checking against tol
zero_range(100000 * c(1, 1 + eps))
#>  TRUE
zero_range(100000 * c(1, 1 + 1001 * eps))
#>  FALSE
zero_range(.00001 * c(1, 1 + eps))
#>  TRUE
zero_range(.00001 * c(1, 1 + 1001 * eps))
#>  FALSE

# NA values
zero_range(c(1, NA)) # NA
#>  NA
zero_range(c(1, NaN)) # NA
#>  NA

# Infinite values
zero_range(c(1, Inf)) # FALSE
#>  FALSE
zero_range(c(-Inf, Inf)) # FALSE
#>  FALSE
zero_range(c(Inf, Inf)) # TRUE
#>  TRUE