topic Re: Round Function Question in SAS Procedures

Round Function Question

milts — Thu, 18 Oct 2012 08:13:45 GMT

Hi Experts,

Would like to consult regarding the round function.

Given the value 123.456 for a, how come this turns out to be the value when I use the round function.

ROUND parameter a = 123.456	Result
b = round(a,0.01)	123.46 (ok)
b = round(a,0.02)	123.46 (ok)
b = round(a,0.03)	123.45 (?)
b = round(a,0.04)	123.44 (?)
b = round(a,0.05)	123.45 (?)
b = round(a,0.06)	123.48 (?)
b = round(a,0.07)	123.48 (?)
b = round(a,0.08)	123.44 (?)
b = round(a,0.09)	123.48 (?)

Is there a bug on the round function or is there something I am not aware on how it derives into these results. Thanks!

Re: Round Function Question

RichardinOz — Thu, 18 Oct 2012 09:36:17 GMT

The second number in the SAS round function specifies the units that should be rounded to, so for example round(123.456, .03) says round the number to the nearest multiple of .03 . There are 4115.2 multiples of .03 in the number 123.456; rounding this to the nearest integer gives 4115 multiples. Multiplying back correctly gives the resultant 123.45, and so for the other values of rounding unit.

Initial value	Rounding Unit	Number of Multiples	Multiples Rounded	Multiplied back
123.456	0.01	12345.6	12346	123.46
123.456	0.02	6172.8	6173	123.46
123.456	0.03	4115.2	4115	123.45
123.456	0.04	3086.4	3086	123.44
123.456	0.05	2469.12	2469	123.45
123.456	0.06	2057.6	2058	123.48
123.456	0.07	1763.657143	1764	123.48
123.456	0.08	1543.2	1543	123.44
123.456	0.09	1371.733333	1372	123.48

Re: Round Function Question

Haikuo — Thu, 18 Oct 2012 18:06:32 GMT

Wow, This is awesome! I did not know that. Learn some. Thanks a lot!

Haikuo

Re: Round Function Question

milts — Fri, 19 Oct 2012 05:52:50 GMT

This is totally great explanation regarding the round function. I believe most are not also aware of this. Thank you very much! You have just expanded my knowledge!

Re: Round Function Question

RichardinOz — Fri, 19 Oct 2012 06:47:02 GMT

I can envisage there might be a situation where round(x, .02) or round(x, .05) might be required but I cannot imagine why anyone would want round(x, .03) or round(x, .07). However, it is there if needed. You can also round to other fractions like quarters, round(x, .25) or eighths, round(x, .125) etc.

Rounding a whole number by say .07 can yield unexpected results: round(123, .07) = 122.99 ( ! ).

milts, thanks for your comment. Can you mark this answered?