Math.Round() call in .NET using negative precision

Question

I have a requirement to perform rounding of values with negative precision. As far as I've checked, Math.Round() in .NET does not support negative precision. For example:

ROUND(43.34566,-1)

The above returns 40.

Please suggest how to achive this.

Negative precision is really just a convention of languages/libraries that support rounding to the nearest 10, 100, etc. Try searching for what you actually want to do. — Jonathon Reinhart, Aug 05 '13 at 07:18
Thanks sashkello. This is working fine even I've adopted same technique,how can we go for generic implementation. Here precision is -1 it might change with diffrent cases. — Girish, Aug 05 '13 at 07:32

score 1 · Answer 1 · answered Aug 05 '13 at 07:17

1

ROUND(43.34566 / 10,0) * 10 will work; generalise as appropriate.

answered Aug 05 '13 at 07:17

Bathsheba

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ROUND(43.34566 / 10,0) * 10 – sashkello Aug 05 '13 at 07:17
@sashkello, touche! I've amended; better get that coffee... – Bathsheba Aug 05 '13 at 07:18

score 1 · Answer 2 · answered Aug 05 '13 at 07:19

1

Quite simple really:

Math.Round(num / Math.Pow(10.0, -(precision))) * Math.Pow(10.0, -(precision));
//this won't work for positives but oh well

answered Aug 05 '13 at 07:19

It'sNotALie.

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Because you probably mean 10 to the power of precision. Then it'll work... – sashkello Aug 05 '13 at 07:21
@sashkello Yep, fixed. – It'sNotALie. Aug 05 '13 at 07:37

score 1 · Accepted Answer · answered Aug 05 '13 at 07:23

Move the comma to the precision you want to give back and then round.

        double n = 43.34566;
        double roundingValue = -1;
        double precision = Math.Pow(10, roundingValue);
        n *= precision;
        double result  = Math.Round(n, 0) / precision;

Math.Round() call in .NET using negative precision

3 Answers3