Check decimal significant figure

Question

I want to check if a decimal has a value in the 4th significant figure.

//3 Significant figures
var val = 1.015;

//4 Significant figures
var val2 = 1.0155;

How can I test to see when there is a value in the 4th significant place.

I want to conditionaly display 3 or 4 decimal places depending if there is a non zero value in the 4th place.

What is the best way to do this?

Would this method work?

if((val * 10000) % 10 != 0) ...

related: http://stackoverflow.com/q/16083666/380384 – John Alexiou Nov 26 '13 at 00:38 — John Alexiou, Nov 26 '13 at 00:38

Sudhakar Tillapudi · Answer 1 · 2013-11-26T00:27:33.830

1.Multiply the value with 1000 and then do (value%10) mod 10 for getting last digit in 3rd significant value .

Example : (3rd significant)

        var val = 1.015;
        int val1=Convert.ToInt32(val * 1000);
        Console.WriteLine(val1 %10); 

Output: 5

2.Multiply the value with 10000 and then do (value%10) mod 10for getting last digit in 4 significant value

Example : (4th significant)

        var val = 1.0157;
        int val1=Convert.ToInt32(val * 10000);
        Console.WriteLine(val1 %10);

Output: 7

score 1 · Answer 2 · answered Nov 26 '13 at 00:16

To learn about formatting your output check this out http://msdn.microsoft.com/en-us/library/kfsatb94(v=vs.110).aspx

To just check if there are 4 or more significant digits you can do

 if (inputString.Split('.')[1].Length > 3)

Of course, that isn't doing any error checking an could easily throw some exceptions but no need to clutter my answer with some basic bounds and nullity checks.

score 1 · Answer 3 · answered Nov 26 '13 at 00:27

1

You can do this with a custom format string:

double d = 1.2340;
string strDouble = d.ToString("0.000#");

answered Nov 26 '13 at 00:27

MarkPflug

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Noctis · Accepted Answer · 2013-11-26T00:43:06.343

The silly answer would be: find the location of the . in your string, and then check the location+4.

The more serious would be, have a look at the double formatting options :)

You could use this formatting of double

//       using the   F4:                    1054.3224

and then if the last index of your string is 0, cut it out using substring.

As of your last edit (if((val * 10000) % 10 != 0) ...), yes, it should work ... Sudhakar suggested the same in his answer.

You should probably take whichever solution you go with, and put it in a helper method that returns an int, and then you can just use that in your code, helping your readability, and reusalibilyt :)

Go with Marks solution, simplest I guess.

double d = 3.40;
Console.Out.WriteLine("d 0.0: {0}", d);                     // 3.4
Console.Out.WriteLine("d 0.0: {0}", d.ToString("0.0"));     // 3.4
Console.Out.WriteLine("d 0.00: {0}", d.ToString("0.00"));   // 3.40
Console.Out.WriteLine("d 0.0#: {0}", d.ToString("0.0#"));   // 3.4

Do notice that if all you have is 3 or 4 digts after the ., the default would be truncated and removed as you can see if the first output above.

Check decimal significant figure

4 Answers4