my doubles get not rounded as expected. Simple example:
int b = 23;
double DurchflussAktBit = 99.5;
double bDurchfluss = 0;
bDurchfluss = DurchflussAktBit * Convert.ToDouble(b) / (double)60;
Math.Round(bDurchfluss, 2);
I get the value 38.141666666666666 for bDurchfluss even after the rounding, I expect the value 38.14. Also tried Math.Round((decimal)bDurchfluss, 2); but gives me the same value.
Where is the error in my code?
Math.Round returns the rounded number - it does not update the number you passed it.
You need to take the return value and assign it to your variable:
bDurchfluss = DurchflussAktBit * Convert.ToDouble(b) / (double)60;
bDurchfluss = Math.Round(bDurchfluss, 2);
Related
This simple calculation is returning zero, I can't figure it out:
decimal share = (18 / 58) * 100;
You are working with integers here. Try using decimals for all the numbers in your calculation.
decimal share = (18m / 58m) * 100m;
18 / 58 is an integer division, which results in 0.
If you want decimal division, you need to use decimal literals:
decimal share = (18m / 58m) * 100m;
Since some people are linking to this from pretty much any thread where the calculation result is a 0, I am adding this as a solution as not all the other answers apply to case scenarios.
The concept of needing to do calculations on various types in order to obtain that type as a result applies, however above only shows 'decimal' and uses it's short form such as 18m as one of the variables to be calculated.
// declare and define initial variables.
int x = 0;
int y = 100;
// set the value of 'x'
x = 44;
// Results in 0 as the whole number 44 over the whole number 100 is a
// fraction less than 1, and thus is 0.
Console.WriteLine( (x / y).ToString() );
// Results in 0 as the whole number 44 over the whole number 100 is a
// fraction less than 1, and thus is 0. The conversion to double happens
// after the calculation has been completed, so technically this results
// in 0.0
Console.WriteLine( ((double)(x / y)).ToString() );
// Results in 0.44 as the variables are cast prior to calculating
// into double which allows for fractions less than 1.
Console.WriteLine( ((double)x / (double)y).ToString() );
Because the numbers are integers and you perform integer division.
18 / 58 is 0 in integer division.
Whenever I encounter such situations, I just upcast the numerator.
double x = 12.0 / 23409;
decimal y = 12m / 24309;
Console.WriteLine($"x = {x} y = {y}");
double res= (firstIntVar * 100f / secondIntVar) / 100f;
when dividing numbers I use double or decimal , else I am getting 0 , with this code even if firstIntVar && secondIntVar are int it will return the expected answer
decimal share = (18 * 100)/58;
Solved: working perfectly with me
int a = 375;
int b = 699;
decimal ab = (decimal)a / b * 100;
This simple calculation is returning zero, I can't figure it out:
decimal share = (18 / 58) * 100;
You are working with integers here. Try using decimals for all the numbers in your calculation.
decimal share = (18m / 58m) * 100m;
18 / 58 is an integer division, which results in 0.
If you want decimal division, you need to use decimal literals:
decimal share = (18m / 58m) * 100m;
Since some people are linking to this from pretty much any thread where the calculation result is a 0, I am adding this as a solution as not all the other answers apply to case scenarios.
The concept of needing to do calculations on various types in order to obtain that type as a result applies, however above only shows 'decimal' and uses it's short form such as 18m as one of the variables to be calculated.
// declare and define initial variables.
int x = 0;
int y = 100;
// set the value of 'x'
x = 44;
// Results in 0 as the whole number 44 over the whole number 100 is a
// fraction less than 1, and thus is 0.
Console.WriteLine( (x / y).ToString() );
// Results in 0 as the whole number 44 over the whole number 100 is a
// fraction less than 1, and thus is 0. The conversion to double happens
// after the calculation has been completed, so technically this results
// in 0.0
Console.WriteLine( ((double)(x / y)).ToString() );
// Results in 0.44 as the variables are cast prior to calculating
// into double which allows for fractions less than 1.
Console.WriteLine( ((double)x / (double)y).ToString() );
Because the numbers are integers and you perform integer division.
18 / 58 is 0 in integer division.
Whenever I encounter such situations, I just upcast the numerator.
double x = 12.0 / 23409;
decimal y = 12m / 24309;
Console.WriteLine($"x = {x} y = {y}");
double res= (firstIntVar * 100f / secondIntVar) / 100f;
when dividing numbers I use double or decimal , else I am getting 0 , with this code even if firstIntVar && secondIntVar are int it will return the expected answer
decimal share = (18 * 100)/58;
Solved: working perfectly with me
int a = 375;
int b = 699;
decimal ab = (decimal)a / b * 100;
This simple calculation is returning zero, I can't figure it out:
decimal share = (18 / 58) * 100;
You are working with integers here. Try using decimals for all the numbers in your calculation.
decimal share = (18m / 58m) * 100m;
18 / 58 is an integer division, which results in 0.
If you want decimal division, you need to use decimal literals:
decimal share = (18m / 58m) * 100m;
Since some people are linking to this from pretty much any thread where the calculation result is a 0, I am adding this as a solution as not all the other answers apply to case scenarios.
The concept of needing to do calculations on various types in order to obtain that type as a result applies, however above only shows 'decimal' and uses it's short form such as 18m as one of the variables to be calculated.
// declare and define initial variables.
int x = 0;
int y = 100;
// set the value of 'x'
x = 44;
// Results in 0 as the whole number 44 over the whole number 100 is a
// fraction less than 1, and thus is 0.
Console.WriteLine( (x / y).ToString() );
// Results in 0 as the whole number 44 over the whole number 100 is a
// fraction less than 1, and thus is 0. The conversion to double happens
// after the calculation has been completed, so technically this results
// in 0.0
Console.WriteLine( ((double)(x / y)).ToString() );
// Results in 0.44 as the variables are cast prior to calculating
// into double which allows for fractions less than 1.
Console.WriteLine( ((double)x / (double)y).ToString() );
Because the numbers are integers and you perform integer division.
18 / 58 is 0 in integer division.
Whenever I encounter such situations, I just upcast the numerator.
double x = 12.0 / 23409;
decimal y = 12m / 24309;
Console.WriteLine($"x = {x} y = {y}");
double res= (firstIntVar * 100f / secondIntVar) / 100f;
when dividing numbers I use double or decimal , else I am getting 0 , with this code even if firstIntVar && secondIntVar are int it will return the expected answer
decimal share = (18 * 100)/58;
Solved: working perfectly with me
int a = 375;
int b = 699;
decimal ab = (decimal)a / b * 100;
In Visual studio 2010, c# .net while doing programming i found that the expressions
var prs1 = (e.X * 100) / panel4.Width;
var prs2 = prs1;
var ans = (prs2 * panel2.Width) / 100;
pb2.Location = new Point(ans, 30);
and another code:
var prs1 = (e.X / panel4.Width) * 100;
var prs2 = prs1;
var ans = (prs2 /100) * panel2.Width;
pb2.Location = new Point(ans, 30);
//this code giving incorrect response
please tell as mathematically both code are equal than why compiler is not giving me same output?
e.X looks like a X coordinate of an event handler. This is an integer value. The same for the .Width property.
Dividing value first may result in loss of precision, especially if the integer division results in 0. Multiplying by 100 afterwards still results in 0.
If you multiply by 100 first, it is more likely that the division is different to 0.
The problem here is rounding.
First part (e.X / panel4.width) of your second code very likely gives 0 as result:
lets say:
e.X = 40 and panel4.width = 250
then you get :
pr1 = (e.X / panel4.width); // 0.16 then it is rounding to 0
pr1 = pr1 * 100 // result is 0
You need to convert your values to double to get result of double then you can convert to "int" yourself later.
pr1 = Convert.ToDouble(e.X) / Convert.ToDouble(panel1.Width) * 100; // result is 16.0
Your problem is not relate to airthmetic expression. Its just because of var keyword.var is used like as generic types.if you initialize val like as int then you can not insert any string value in that or may be something else.
you got var ans like as double or int and you pass this to [pb2.Location = new Point(ans, 30);] which is wrong.because point relate to another type.
I have tried using Math.Round & MidpointRounding. This does not appear to do what I need.
Example:
52.34567 rounded to 2 decimals UP = 52.35
1.183 rounded to 2 decimals DOWN = 1.18
Do I need to write a custom function?
Edit:
I should have been more specific.
Sometimes I need a number like 23.567 to round DOWN to 23.56.
In this scenario...
Math.Round(dec, 2, MidpointRounding.AwayFromZero) gives 23.57
Math.Round(dec, 2, MidpointRounding.ToEven) gives 23.57
Decimals up to 9 decimal places could come out and need to be rounded to 1, 2, 3 or even 4 decimal places.
Try using decimal.Round():
decimal.Round(x, 2)
Where x is your value and 2 is the number of decimals you wish to keep.
You can also specify whether .5 rounds up or down by passing third parameter:
decimal.Round(x, 2, MidpointRounding.AwayFromZero);
EDIT:
In light of the new requirement (i.e. that numbers are sometimes rounded down despite being greater than "halfway" to the next interval), you can try:
var pow = Math.Pow(10, numDigits);
var truncated = Math.Truncate(x*pow) / pow;
Truncate() lops off the non-integer portion of the decimal. Note that numDigits above should be how many digits you want to KEEP, not the total number of decimals, etc.
Finally, if you want to force a round up (truncation really is a forced round-down), you would just add 1 to the result of the Truncate() call before dividing again.
Try using Math.Ceiling (up) or Math.Floor (down). e.g Math.Floor(1.8) == 1.
Assuming you're using the decimal type for your numbers,
static class Rounding
{
public static decimal RoundUp(decimal number, int places)
{
decimal factor = RoundFactor(places);
number *= factor;
number = Math.Ceiling(number);
number /= factor;
return number;
}
public static decimal RoundDown(decimal number, int places)
{
decimal factor = RoundFactor(places);
number *= factor;
number = Math.Floor(number);
number /= factor;
return number;
}
internal static decimal RoundFactor(int places)
{
decimal factor = 1m;
if (places < 0)
{
places = -places;
for (int i = 0; i < places; i++)
factor /= 10m;
}
else
{
for (int i = 0; i < places; i++)
factor *= 10m;
}
return factor;
}
}
Example:
Rounding.RoundDown(23.567, 2) prints 23.56
For a shorter version of the accepted answer, here are the RoundUp and RoundDown functions that can be used:
public double RoundDown(double number, int decimalPlaces)
{
return Math.Floor(number * Math.Pow(10, decimalPlaces)) / Math.Pow(10, decimalPlaces);
}
public double RoundUp(double number, int decimalPlaces)
{
return Math.Ceiling(number * Math.Pow(10, decimalPlaces)) / Math.Pow(10, decimalPlaces);
}
Complete code with result.
double a = Math.Round(128.5, 0, MidpointRounding.AwayFromZero);
Result is 129
The Math class gives you methods to use to round up and down, they are Math.Ceiling() and Math.Floor() respectively. They work like Math.Round(), but they have a particularity, they only receive a value and round them to only the entire part.
So you need to use Math.Pow() to multiply the value by 10 to the n-esimal units you need to round power and then you need to divide by the same multiplied value.
Is important that you note, that the input parameters of the Math.Pow() method are double, so you need to convert them to double.
For example:
When you want to round up the value to 3 decimals (supposing value type is decimal):
double decimalsNumber = 3;
decimal valueToRound = 1.1835675M;
// powerOfTen must be equal to 10^3 or 1000.
double powerOfTen = Math.Pow(10, decimalsNumber);
// rounded must be equal to Math.Ceiling(1.1835675 * 1000) / 1000
decimal rounded = Math.Ceiling(valueToRound * (decimal)powerOfTen) / (decimal)powerOfTen;
Result: rounded = 1.184
When you want to round down the value to 3 decimals (supposing value type is decimal):
double decimalsNumber = 3;
decimal valueToRound = 1.1835675M;
// powerOfTen must be equal to 10^3 or 1000.
double powerOfTen = Math.Pow(10, decimalsNumber);
// rounded must be equal to Math.Floor(1.1835675 * 1000) / 1000
decimal rounded = Math.Floor(valueToRound * (decimal)powerOfTen) / (decimal)powerOfTen;
Result: rounded = 1.183
To reference how to use them more specificaly and to get more information and about both methods you can see these pages from the oficial MSDN Microsoft site:
Math Class
Math.Pow Method (Double, Double)
Math.Floor Method (Decimal)
Math.Floor Method (Double)
Math.Ceiling Method (Decimal)
Math.Ceiling Method (Double)
try this custom rounding
public int Round(double value)
{
double decimalpoints = Math.Abs(value - Math.Floor(value));
if (decimalpoints > 0.5)
return (int)Math.Round(value);
else
return (int)Math.Floor(value);
}
Maybe this?
Math.Round(dec + 0.5m, MidpointRounding.AwayFromZero);
You can achieve that by using the Method of Math.Round() or decimal.Round()-:
Math.Round(amt)
Math.Round(amt, Int32) and other overloading methods.
decimal.Round(amt)
decimal.Round(amt, 2) and other overloding methods.