Round up from .5

Question

Yes I know why we always round to the nearest even number if we are in the exact middle (i.e. 2.5 becomes 2) of two numbers. But when I want to evaluate data for some people they don't want this behaviour. What is the simplest method to get this:

x <- seq(0.5,9.5,by=1) round(x) 

to be 1,2,3,...,10 and not 0,2,2,4,4,...,10.

Edit: To clearify: 1.4999 should be 1 after rounding. (I thought this would be obvious)

Answer 1

This is not my own function, and unfortunately, I can't find where I got it at the moment (originally found as an anonymous comment at the Statistically Significant blog), but it should help with what you need.

round2 = function(x, n) {   posneg = sign(x)   z = abs(x)*10^n   z = z + 0.5 + sqrt(.Machine$double.eps)   z = trunc(z)   z = z/10^n   z*posneg } 

x is the object you want to round, and n is the number of digits you are rounding to.

An Example

x = c(1.85, 1.54, 1.65, 1.85, 1.84) round(x, 1) # [1] 1.8 1.5 1.6 1.8 1.8 round2(x, 1) # [1] 1.9 1.5 1.7 1.9 1.8 

(Thanks @Gregor for the addition of + sqrt(.Machine$double.eps).)

Answer 2

If you want something that behaves exactly like round except for those xxx.5 values, try this:

x <- seq(0, 1, 0.1) x # [1] 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 floor(0.5 + x) # [1] 0 0 0 0 0 1 1 1 1 1 1