Trimming a float

Question

Possible Duplicate:
Leave only two decimal places after the dot
Formatting a float to 2 decimal places

If I have a float that consists of something like 153.2154879, is there any way to convert it to string but only show 4 decimal places? I know I can format it using "000.000", but the front number doesnt always have to be 3 digits. So is there a way to show all the front numbers (153), but only the first 4 characters after the point in a string?

possible duplicate: http://stackoverflow.com/q/1291483/962091 — zackdever, Apr 17 '12 at 18:10

Icarus · Answer 1 · 2012-04-17T18:36:20.423

8

Something like this should do:

your_number.ToString("0.####");

This will show a max of 4 decimal places.

edited Apr 17 '12 at 18:36

answered Apr 17 '12 at 18:03

Icarus

63,293
14
100
115

`your_number.ToString("0.####")` would be more efficient, as well as offering culture-sensitive overloads. – phoog Apr 17 '12 at 18:22
-1. Converting a float to string and then back to float just to **round it** makes no sense. – Aliostad Apr 17 '12 at 18:28
@Aliostad rounding and truncating are 2 different things. Formatting a number 2 a max of 4 decimal places is not rounding. I updated my answer to include a more "efficient approach" as suggested by phoog. – Icarus Apr 17 '12 at 18:40

Justin · Accepted Answer · 2012-04-18T11:37:45.357

7

I usually use a format string like "#0.0000".

edited Apr 18 '12 at 11:37

answered Apr 17 '12 at 18:02

Justin

6,611
3
36
57

So the `#` just means show all the characters? Never knew about this thanks! – TheGateKeeper Apr 17 '12 at 18:06
-1. Converting a float to string and then back to float just to **round it** makes no sense. – Aliostad Apr 17 '12 at 18:28
Why are you going around downvoting everyone Aliostad? I clearly stated I wanted to show 4 decimal places, I never said I wanted to round it and convert it back to float! – TheGateKeeper Apr 17 '12 at 18:32
@Aliostad where are we converting the number back to float? – phoog Apr 17 '12 at 18:42
Sorry guys my bad. Can you edit your answer so I can make my downvote upvote? – Aliostad Apr 17 '12 at 18:56

score 5 · Answer 3 · answered Apr 17 '12 at 18:04

5

You can use the C# function Math.Round function.

float a= 153.213456; Math.Round(a,3); this would round up the number to 153.213 then get convert it to string.

answered Apr 17 '12 at 18:04

Lukasz Bator

121
5

The string formatting code is going to round the number again; there's no reason to call Math.Round first. – phoog Apr 17 '12 at 18:23
@phoog Do you mean you convert the float to string and then convert back to float and not use the Round which is designed for the float?? – Aliostad Apr 17 '12 at 18:27
@Aliostad of course not! The question is about *displaying* a float with a given number of decimal points, which means *converting it to a string* with that number of decimal points. I mean that *it is inefficient to use `Round` for the purpose of formatting a number for display.* If the requirement is to have a rounded `float` in IEEE single binary format, for storage or calculation, then of course you should use `Round`. – phoog Apr 17 '12 at 18:41
@phoog I think Aliostad confuses truncating with rounding. See his comment to my answer. – Icarus Apr 17 '12 at 18:42

Trimming a float

3 Answers3