This question already has answers here:
C# midpointrounding down to zero
(3 answers)
Closed 4 years ago.
If I have a double, and want to round it down to the nearest quarter value (0.25), is this possible?
Each of these give me 0.5 and should actually give me 0.25:
Math.Round(0.499999, 2, MidpointRounding.AwayFromZero);
Math.Round(0.499999, 2, MidpointRounding.ToEven);
Is there any notion of always rounding "down"?
This question is related to "nearest" rounding. I don't need that
The "duplicate" is entirely based on NEAREST rounding. that is utterly irrelevant to me. I am not asking about NEAREST. I am asking about always rounding DOWN. Notice that 0.499999 is very NEAR to 0.5 - and that is not what I want. I want 0.49999 to become 0.25 (DOWN)
double x = 0.4999;
double answer = Math.Truncate(4*x)/4; // result: 0.25
Related
This question already has answers here:
Is floating point math broken?
(31 answers)
Closed 2 years ago.
for (double i = 0; i < 0.05; i+= 0.001)
{
//do something
}
In this for loop,
I thought the count would go as follows: 0, 0.001, 0.002, 0.003, etc., but it becomes 0.0090000000000000011 instead of 0.009.
Why is such conversion possible?
The resolution of the double/float is not infinite.
See here
Because some numbers cannot be represented exactly as fractional binary values, floating-point numbers can only approximate real numbers.
This question already has answers here:
Truncate Two decimal places without rounding
(24 answers)
Closed 4 years ago.
For example if I divide 1050 / 256 I get 4.1015625. I need the value of first digit after decimal point (1 in this case). I don't want to involve ToString() conversions and then parsing it into digit again.
This picture for itsme86:
This picture for Jeroen Mostert:
What about:
decimal result = 4.1015625m;
result = result - (int)result;
result = Decimal.Round(result, 1, MidpointRounding.AwayFromZero);
This can be combined into one line if needed but is more readable this way.
Math.Floor((4.1015625 - Math.Floor(4.1015625)) * 10)
I would do it this way:
First i would subtract the the number before the decimal seperator of the given number.
Then I would multiply it by 10.
Example: 4.2 - 4 = .2 * 10 = 2
NOTE: You cannot use floating point numbers for accurate mathematical operations, as some values cannot be represented properly. So always cast to/use decimal and not float/double if you need exact values like this.
This question already has answers here:
Is floating point math broken?
(31 answers)
Closed 7 years ago.
AFAIK .NET's default round option is to even, so Math.Round(1.225,2) should give 1.22 but it gives 1.23.
Math.Round(2.225,2) = 2.22
Math.Round(100.225,2) = 100.22
all the values I tried rounds to nearest even but only 1.225 and -1.225 rounds to 1.23 and -1.23.
The main problem is that in float and double, the amount of decimal places is not part of the value, and the precision isn't decimal, but rather, binary. And there's no finite binary number that can represent 1.225 exactly.
So when you do Math.Round(1.225f, 2), you're actually doing something more like Math.Round(1.22500002f, 2) - there's no midpoint rounding involved.
The same problem appears with Math.Round(2.225f, 2) - it's just that the "real" value is slightly smaller than 2.225f, so the result rounds down. But there's still no midpoint rounding involved.
If you need decimal precision, use decimal. Neither float nor double are designed for decimal precision - they're fine for e.g. physics calculations, but not for e.g. accounting.
1.225 can't be represented exactly in floating point, so you're really rounding 1.225000023841858.
This question already has answers here:
Double vs Decimal Rounding in C#
(2 answers)
Closed 7 years ago.
I am doing following equation but the result is not as expected
double dasdas = Math.Abs(3.2 - 1.9);
The result is
1.3000000000000003
However the correct result should be
1.3
What may be the reason of this?
c# 4.5.2
This is because you're using a double - which is a floating point. These by definition this cannot store the exact number.
You need to use Decimal.
Take at look at here and What Every Computer Scientist Should Read About Floating Point
Use decimal:
decimal dasdas = Math.Abs(3.2m - 1.9m);
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
What's wrong with this division?
If you divide 2 / 3, it should return 0.66666666666666667. Instead, I get 0.0 in double value type and 0 in decimal.
My purpose is to divide even (e.g. 2 / 3) and round to 1 always to the nearest.
Any help?
You're doing integer division, from the sounds of it. Try this:
decimal result = 2.0 / 3.0;
Or even force it to decimals for all of the operations:
decimal result = 2.0m / 3.0m;
This should give you a result more like you expect.
Doing 2/3 is integer division which will not return the decimal place of the division. To get .666666667 you will need to do 2.0 / 3.0 which are both doubles to get the expected answer.