Formatieren von Zahlen mit signifikanten Zahlen in C #
https://stackoverflow.com/questions/158172
-
03-07-2019 - |
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Ich habe einige Dezimal-Daten, die ich in eine Sharepoint-Liste am drängen, wo es gesehen werden. Ich möchte die Anzahl der signifikanten Zahlen in den Ergebnisdaten der spezifischen Berechnung auf Basis meines Wissens angezeigt beschränken. Manchmal wird es 3 sein, so wird 12345 12300 werden und 0,012345 wird 0,0123 geworden. Gelegentlich wird es 4 oder 5. Gibt es eine bequeme Möglichkeit, dies zu umgehen?
Lösung
Siehe auch: RoundToSignificantFigures von "P Daddy".
Ich habe seine Methode mit einem anderen kombiniert ich mochte.
Rundung auf signifikante Zahlen ist viel einfacher, in TSQL, wo die Rundungsmethode auf Rundungsposition basiert, nicht Anzahl der Dezimalstellen - was der Fall mit .Net Math.round ist. Sie könnten eine Zahl in TSQL zu negativen Plätze Runde, die auf ganze Zahlen Runde würde -. So die Skalierung ist nicht erforderlich
Siehe auch diese anderer Thread . Pyrolistical Methode ist gut.
Der nachfolgenden Nullen Teil des Problems scheint eher eine String-Operation zu mir, so enthalten ich eine ToString () Erweiterungsmethode die Pad Nullen, falls erforderlich.
using System;
using System.Globalization;
public static class Precision
{
// 2^-24
public const float FLOAT_EPSILON = 0.0000000596046448f;
// 2^-53
public const double DOUBLE_EPSILON = 0.00000000000000011102230246251565d;
public static bool AlmostEquals(this double a, double b, double epsilon = DOUBLE_EPSILON)
{
// ReSharper disable CompareOfFloatsByEqualityOperator
if (a == b)
{
return true;
}
// ReSharper restore CompareOfFloatsByEqualityOperator
return (System.Math.Abs(a - b) < epsilon);
}
public static bool AlmostEquals(this float a, float b, float epsilon = FLOAT_EPSILON)
{
// ReSharper disable CompareOfFloatsByEqualityOperator
if (a == b)
{
return true;
}
// ReSharper restore CompareOfFloatsByEqualityOperator
return (System.Math.Abs(a - b) < epsilon);
}
}
public static class SignificantDigits
{
public static double Round(this double value, int significantDigits)
{
int unneededRoundingPosition;
return RoundSignificantDigits(value, significantDigits, out unneededRoundingPosition);
}
public static string ToString(this double value, int significantDigits)
{
// this method will round and then append zeros if needed.
// i.e. if you round .002 to two significant figures, the resulting number should be .0020.
var currentInfo = CultureInfo.CurrentCulture.NumberFormat;
if (double.IsNaN(value))
{
return currentInfo.NaNSymbol;
}
if (double.IsPositiveInfinity(value))
{
return currentInfo.PositiveInfinitySymbol;
}
if (double.IsNegativeInfinity(value))
{
return currentInfo.NegativeInfinitySymbol;
}
int roundingPosition;
var roundedValue = RoundSignificantDigits(value, significantDigits, out roundingPosition);
// when rounding causes a cascading round affecting digits of greater significance,
// need to re-round to get a correct rounding position afterwards
// this fixes a bug where rounding 9.96 to 2 figures yeilds 10.0 instead of 10
RoundSignificantDigits(roundedValue, significantDigits, out roundingPosition);
if (Math.Abs(roundingPosition) > 9)
{
// use exponential notation format
// ReSharper disable FormatStringProblem
return string.Format(currentInfo, "{0:E" + (significantDigits - 1) + "}", roundedValue);
// ReSharper restore FormatStringProblem
}
// string.format is only needed with decimal numbers (whole numbers won't need to be padded with zeros to the right.)
// ReSharper disable FormatStringProblem
return roundingPosition > 0 ? string.Format(currentInfo, "{0:F" + roundingPosition + "}", roundedValue) : roundedValue.ToString(currentInfo);
// ReSharper restore FormatStringProblem
}
private static double RoundSignificantDigits(double value, int significantDigits, out int roundingPosition)
{
// this method will return a rounded double value at a number of signifigant figures.
// the sigFigures parameter must be between 0 and 15, exclusive.
roundingPosition = 0;
if (value.AlmostEquals(0d))
{
roundingPosition = significantDigits - 1;
return 0d;
}
if (double.IsNaN(value))
{
return double.NaN;
}
if (double.IsPositiveInfinity(value))
{
return double.PositiveInfinity;
}
if (double.IsNegativeInfinity(value))
{
return double.NegativeInfinity;
}
if (significantDigits < 1 || significantDigits > 15)
{
throw new ArgumentOutOfRangeException("significantDigits", value, "The significantDigits argument must be between 1 and 15.");
}
// The resulting rounding position will be negative for rounding at whole numbers, and positive for decimal places.
roundingPosition = significantDigits - 1 - (int)(Math.Floor(Math.Log10(Math.Abs(value))));
// try to use a rounding position directly, if no scale is needed.
// this is because the scale mutliplication after the rounding can introduce error, although
// this only happens when you're dealing with really tiny numbers, i.e 9.9e-14.
if (roundingPosition > 0 && roundingPosition < 16)
{
return Math.Round(value, roundingPosition, MidpointRounding.AwayFromZero);
}
// Shouldn't get here unless we need to scale it.
// Set the scaling value, for rounding whole numbers or decimals past 15 places
var scale = Math.Pow(10, Math.Ceiling(Math.Log10(Math.Abs(value))));
return Math.Round(value / scale, significantDigits, MidpointRounding.AwayFromZero) * scale;
}
}
Andere Tipps
Dies könnte den Trick tun:
double Input1 = 1234567;
string Result1 = Convert.ToDouble(String.Format("{0:G3}",Input1)).ToString("R0");
double Input2 = 0.012345;
string Result2 = Convert.ToDouble(String.Format("{0:G3}", Input2)).ToString("R6");
, um die G3 bis G4 Änderung erzeugt das merkwürdigste Ergebnis though. Es scheint, die signifikanten Stellen abzurunden?
Ich landete einige Code Verhaken von http://ostermiller.org/utils/SignificantFigures. java.html . Es war in Java, so habe ich eine schnelle Suchen / Ersetzen und einige resharper Neuformatierung der C # Build zu machen. Es scheint für meine bedeutende Figur Bedürfnisse gut zu funktionieren. FWIW, nahm ich seine javadoc Kommentare hier prägnanter zu machen, aber der ursprüngliche Code ist recht gut dokumentiert.
/*
* Copyright (C) 2002-2007 Stephen Ostermiller
* http://ostermiller.org/contact.pl?regarding=Java+Utilities
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* See COPYING.TXT for details.
*/
public class SignificantFigures
{
private String original;
private StringBuilder _digits;
private int mantissa = -1;
private bool sign = true;
private bool isZero = false;
private bool useScientificNotation = true;
public SignificantFigures(String number)
{
original = number;
Parse(original);
}
public SignificantFigures(double number)
{
original = Convert.ToString(number);
try
{
Parse(original);
}
catch (Exception nfe)
{
_digits = null;
}
}
public bool UseScientificNotation
{
get { return useScientificNotation; }
set { useScientificNotation = value; }
}
public int GetNumberSignificantFigures()
{
if (_digits == null) return 0;
return _digits.Length;
}
public SignificantFigures SetLSD(int place)
{
SetLMSD(place, Int32.MinValue);
return this;
}
public SignificantFigures SetLMSD(int leastPlace, int mostPlace)
{
if (_digits != null && leastPlace != Int32.MinValue)
{
int significantFigures = _digits.Length;
int current = mantissa - significantFigures + 1;
int newLength = significantFigures - leastPlace + current;
if (newLength <= 0)
{
if (mostPlace == Int32.MinValue)
{
original = "NaN";
_digits = null;
}
else
{
newLength = mostPlace - leastPlace + 1;
_digits.Length = newLength;
mantissa = leastPlace;
for (int i = 0; i < newLength; i++)
{
_digits[i] = '0';
}
isZero = true;
sign = true;
}
}
else
{
_digits.Length = newLength;
for (int i = significantFigures; i < newLength; i++)
{
_digits[i] = '0';
}
}
}
return this;
}
public int GetLSD()
{
if (_digits == null) return Int32.MinValue;
return mantissa - _digits.Length + 1;
}
public int GetMSD()
{
if (_digits == null) return Int32.MinValue;
return mantissa + 1;
}
public override String ToString()
{
if (_digits == null) return original;
StringBuilder digits = new StringBuilder(this._digits.ToString());
int length = digits.Length;
if ((mantissa <= -4 || mantissa >= 7 ||
(mantissa >= length &&
digits[digits.Length - 1] == '0') ||
(isZero && mantissa != 0)) && useScientificNotation)
{
// use scientific notation.
if (length > 1)
{
digits.Insert(1, '.');
}
if (mantissa != 0)
{
digits.Append("E" + mantissa);
}
}
else if (mantissa <= -1)
{
digits.Insert(0, "0.");
for (int i = mantissa; i < -1; i++)
{
digits.Insert(2, '0');
}
}
else if (mantissa + 1 == length)
{
if (length > 1 && digits[digits.Length - 1] == '0')
{
digits.Append('.');
}
}
else if (mantissa < length)
{
digits.Insert(mantissa + 1, '.');
}
else
{
for (int i = length; i <= mantissa; i++)
{
digits.Append('0');
}
}
if (!sign)
{
digits.Insert(0, '-');
}
return digits.ToString();
}
public String ToScientificNotation()
{
if (_digits == null) return original;
StringBuilder digits = new StringBuilder(this._digits.ToString());
int length = digits.Length;
if (length > 1)
{
digits.Insert(1, '.');
}
if (mantissa != 0)
{
digits.Append("E" + mantissa);
}
if (!sign)
{
digits.Insert(0, '-');
}
return digits.ToString();
}
private const int INITIAL = 0;
private const int LEADZEROS = 1;
private const int MIDZEROS = 2;
private const int DIGITS = 3;
private const int LEADZEROSDOT = 4;
private const int DIGITSDOT = 5;
private const int MANTISSA = 6;
private const int MANTISSADIGIT = 7;
private void Parse(String number)
{
int length = number.Length;
_digits = new StringBuilder(length);
int state = INITIAL;
int mantissaStart = -1;
bool foundMantissaDigit = false;
// sometimes we don't know if a zero will be
// significant or not when it is encountered.
// keep track of the number of them so that
// the all can be made significant if we find
// out that they are.
int zeroCount = 0;
int leadZeroCount = 0;
for (int i = 0; i < length; i++)
{
char c = number[i];
switch (c)
{
case '.':
{
switch (state)
{
case INITIAL:
case LEADZEROS:
{
state = LEADZEROSDOT;
}
break;
case MIDZEROS:
{
// we now know that these zeros
// are more than just trailing place holders.
for (int j = 0; j < zeroCount; j++)
{
_digits.Append('0');
}
zeroCount = 0;
state = DIGITSDOT;
}
break;
case DIGITS:
{
state = DIGITSDOT;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case '+':
{
switch (state)
{
case INITIAL:
{
sign = true;
state = LEADZEROS;
}
break;
case MANTISSA:
{
state = MANTISSADIGIT;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case '-':
{
switch (state)
{
case INITIAL:
{
sign = false;
state = LEADZEROS;
}
break;
case MANTISSA:
{
state = MANTISSADIGIT;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case '0':
{
switch (state)
{
case INITIAL:
case LEADZEROS:
{
// only significant if number
// is all zeros.
zeroCount++;
leadZeroCount++;
state = LEADZEROS;
}
break;
case MIDZEROS:
case DIGITS:
{
// only significant if followed
// by a decimal point or nonzero digit.
mantissa++;
zeroCount++;
state = MIDZEROS;
}
break;
case LEADZEROSDOT:
{
// only significant if number
// is all zeros.
mantissa--;
zeroCount++;
state = LEADZEROSDOT;
}
break;
case DIGITSDOT:
{
// non-leading zeros after
// a decimal point are always
// significant.
_digits.Append(c);
}
break;
case MANTISSA:
case MANTISSADIGIT:
{
foundMantissaDigit = true;
state = MANTISSADIGIT;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
{
switch (state)
{
case INITIAL:
case LEADZEROS:
case DIGITS:
{
zeroCount = 0;
_digits.Append(c);
mantissa++;
state = DIGITS;
}
break;
case MIDZEROS:
{
// we now know that these zeros
// are more than just trailing place holders.
for (int j = 0; j < zeroCount; j++)
{
_digits.Append('0');
}
zeroCount = 0;
_digits.Append(c);
mantissa++;
state = DIGITS;
}
break;
case LEADZEROSDOT:
case DIGITSDOT:
{
zeroCount = 0;
_digits.Append(c);
state = DIGITSDOT;
}
break;
case MANTISSA:
case MANTISSADIGIT:
{
state = MANTISSADIGIT;
foundMantissaDigit = true;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
case 'E':
case 'e':
{
switch (state)
{
case INITIAL:
case LEADZEROS:
case DIGITS:
case LEADZEROSDOT:
case DIGITSDOT:
{
// record the starting point of the mantissa
// so we can do a substring to get it back later
mantissaStart = i + 1;
state = MANTISSA;
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
break;
default:
{
throw new Exception(
"Unexpected character '" + c + "' at position " + i
);
}
}
}
if (mantissaStart != -1)
{
// if we had found an 'E'
if (!foundMantissaDigit)
{
// we didn't actually find a mantissa to go with.
throw new Exception(
"No digits in mantissa."
);
}
// parse the mantissa.
mantissa += Convert.ToInt32(number.Substring(mantissaStart));
}
if (_digits.Length == 0)
{
if (zeroCount > 0)
{
// if nothing but zeros all zeros are significant.
for (int j = 0; j < zeroCount; j++)
{
_digits.Append('0');
}
mantissa += leadZeroCount;
isZero = true;
sign = true;
}
else
{
// a hack to catch some cases that we could catch
// by adding a ton of extra states. Things like:
// "e2" "+e2" "+." "." "+" etc.
throw new Exception(
"No digits in number."
);
}
}
}
public SignificantFigures SetNumberSignificantFigures(int significantFigures)
{
if (significantFigures <= 0)
throw new ArgumentException("Desired number of significant figures must be positive.");
if (_digits != null)
{
int length = _digits.Length;
if (length < significantFigures)
{
// number is not long enough, pad it with zeros.
for (int i = length; i < significantFigures; i++)
{
_digits.Append('0');
}
}
else if (length > significantFigures)
{
// number is too long chop some of it off with rounding.
bool addOne; // we need to round up if true.
char firstInSig = _digits[significantFigures];
if (firstInSig < '5')
{
// first non-significant digit less than five, round down.
addOne = false;
}
else if (firstInSig == '5')
{
// first non-significant digit equal to five
addOne = false;
for (int i = significantFigures + 1; !addOne && i < length; i++)
{
// if its followed by any non-zero digits, round up.
if (_digits[i] != '0')
{
addOne = true;
}
}
if (!addOne)
{
// if it was not followed by non-zero digits
// if the last significant digit is odd round up
// if the last significant digit is even round down
addOne = (_digits[significantFigures - 1] & 1) == 1;
}
}
else
{
// first non-significant digit greater than five, round up.
addOne = true;
}
// loop to add one (and carry a one if added to a nine)
// to the last significant digit
for (int i = significantFigures - 1; addOne && i >= 0; i--)
{
char digit = _digits[i];
if (digit < '9')
{
_digits[i] = (char) (digit + 1);
addOne = false;
}
else
{
_digits[i] = '0';
}
}
if (addOne)
{
// if the number was all nines
_digits.Insert(0, '1');
mantissa++;
}
// chop it to the correct number of figures.
_digits.Length = significantFigures;
}
}
return this;
}
public double ToDouble()
{
return Convert.ToDouble(original);
}
public static String Format(double number, int significantFigures)
{
SignificantFigures sf = new SignificantFigures(number);
sf.SetNumberSignificantFigures(significantFigures);
return sf.ToString();
}
}
Ich habe eine kurzgeschlossene Antwort signifikante Zahlen eine Reihe . Hier ist der Code & die Testergebnisse ...
using System;
using System.Collections.Generic;
namespace ConsoleApplicationRound
{
class Program
{
static void Main(string[] args)
{
//char cDecimal = '.'; // for English cultures
char cDecimal = ','; // for German cultures
List<double> l_dValue = new List<double>();
ushort usSignificants = 5;
l_dValue.Add(0);
l_dValue.Add(0.000640589);
l_dValue.Add(-0.000640589);
l_dValue.Add(-123.405009);
l_dValue.Add(123.405009);
l_dValue.Add(-540);
l_dValue.Add(540);
l_dValue.Add(-540911);
l_dValue.Add(540911);
l_dValue.Add(-118.2);
l_dValue.Add(118.2);
l_dValue.Add(-118.18);
l_dValue.Add(118.18);
l_dValue.Add(-118.188);
l_dValue.Add(118.188);
foreach (double d in l_dValue)
{
Console.WriteLine("d = Maths.Round('" +
cDecimal + "', " + d + ", " + usSignificants +
") = " + Maths.Round(
cDecimal, d, usSignificants));
}
Console.Read();
}
}
}
Die verwendete Mathematik Klasse ist wie folgt:
using System;
using System.Text;
namespace ConsoleApplicationRound
{
class Maths
{
/// <summary>
/// The word "Window"
/// </summary>
private static String m_strZeros = "000000000000000000000000000000000";
/// <summary>
/// The minus sign
/// </summary>
public const char m_cDASH = '-';
/// <summary>
/// Determines the number of digits before the decimal point
/// </summary>
/// <param name="cDecimal">
/// Language-specific decimal separator
/// </param>
/// <param name="strValue">
/// Value to be scrutinised
/// </param>
/// <returns>
/// Nr. of digits before the decimal point
/// </returns>
private static ushort NrOfDigitsBeforeDecimal(char cDecimal, String strValue)
{
short sDecimalPosition = (short)strValue.IndexOf(cDecimal);
ushort usSignificantDigits = 0;
if (sDecimalPosition >= 0)
{
strValue = strValue.Substring(0, sDecimalPosition + 1);
}
for (ushort us = 0; us < strValue.Length; us++)
{
if (strValue[us] != m_cDASH) usSignificantDigits++;
if (strValue[us] == cDecimal)
{
usSignificantDigits--;
break;
}
}
return usSignificantDigits;
}
/// <summary>
/// Rounds to a fixed number of significant digits
/// </summary>
/// <param name="d">
/// Number to be rounded
/// </param>
/// <param name="usSignificants">
/// Requested significant digits
/// </param>
/// <returns>
/// The rounded number
/// </returns>
public static String Round(char cDecimal,
double d,
ushort usSignificants)
{
StringBuilder value = new StringBuilder(Convert.ToString(d));
short sDecimalPosition = (short)value.ToString().IndexOf(cDecimal);
ushort usAfterDecimal = 0;
ushort usDigitsBeforeDecimalPoint =
NrOfDigitsBeforeDecimal(cDecimal, value.ToString());
if (usDigitsBeforeDecimalPoint == 1)
{
usAfterDecimal = (d == 0)
? usSignificants
: (ushort)(value.Length - sDecimalPosition - 2);
}
else
{
if (usSignificants >= usDigitsBeforeDecimalPoint)
{
usAfterDecimal =
(ushort)(usSignificants - usDigitsBeforeDecimalPoint);
}
else
{
double dPower = Math.Pow(10,
usDigitsBeforeDecimalPoint - usSignificants);
d = dPower*(long)(d/dPower);
}
}
double dRounded = Math.Round(d, usAfterDecimal);
StringBuilder result = new StringBuilder();
result.Append(dRounded);
ushort usDigits = (ushort)result.ToString().Replace(
Convert.ToString(cDecimal), "").Replace(
Convert.ToString(m_cDASH), "").Length;
// Add lagging zeros, if necessary:
if (usDigits < usSignificants)
{
if (usAfterDecimal != 0)
{
if (result.ToString().IndexOf(cDecimal) == -1)
{
result.Append(cDecimal);
}
int i = (d == 0) ? 0 : Math.Min(0, usDigits - usSignificants);
result.Append(m_strZeros.Substring(0, usAfterDecimal + i));
}
}
return result.ToString();
}
}
}
Jede Antwort mit einem kürzeren Code?
Sie können eine elegante Bit perfekte Abrundung erhalten, indem die GetBITS Methode auf Dezimal Verwendung und Nutzung BigInteger Maskierung auszuführen.
Einige utils
public static int CountDigits
(BigInteger number) => ((int)BigInteger.Log10(number))+1;
private static readonly BigInteger[] BigPowers10
= Enumerable.Range(0, 100)
.Select(v => BigInteger.Pow(10, v))
.ToArray();
Die Hauptfunktion
public static decimal RoundToSignificantDigits
(this decimal num,
short n)
{
var bits = decimal.GetBits(num);
var u0 = unchecked((uint)bits[0]);
var u1 = unchecked((uint)bits[1]);
var u2 = unchecked((uint)bits[2]);
var i = new BigInteger(u0)
+ (new BigInteger(u1) << 32)
+ (new BigInteger(u2) << 64);
var d = CountDigits(i);
var delta = d - n;
if (delta < 0)
return num;
var scale = BigPowers10[delta];
var div = i/scale;
var rem = i%scale;
var up = rem > scale/2;
if (up)
div += 1;
var shifted = div*scale;
bits[0] =unchecked((int)(uint) (shifted & BigUnitMask));
bits[1] =unchecked((int)(uint) (shifted>>32 & BigUnitMask));
bits[2] =unchecked((int)(uint) (shifted>>64 & BigUnitMask));
return new decimal(bits);
}
Testfall 0
public void RoundToSignificantDigits()
{
WMath.RoundToSignificantDigits(0.0012345m, 2).Should().Be(0.0012m);
WMath.RoundToSignificantDigits(0.0012645m, 2).Should().Be(0.0013m);
WMath.RoundToSignificantDigits(0.040000000000000008, 6).Should().Be(0.04);
WMath.RoundToSignificantDigits(0.040000010000000008, 6).Should().Be(0.04);
WMath.RoundToSignificantDigits(0.040000100000000008, 6).Should().Be(0.0400001);
WMath.RoundToSignificantDigits(0.040000110000000008, 6).Should().Be(0.0400001);
WMath.RoundToSignificantDigits(0.20000000000000004, 6).Should().Be(0.2);
WMath.RoundToSignificantDigits(0.10000000000000002, 6).Should().Be(0.1);
WMath.RoundToSignificantDigits(0.0, 6).Should().Be(0.0);
}
Testfall 1
public void RoundToSigFigShouldWork()
{
1.2m.RoundToSignificantDigits(1).Should().Be(1m);
0.01235668m.RoundToSignificantDigits(3).Should().Be(0.0124m);
0.01m.RoundToSignificantDigits(3).Should().Be(0.01m);
1.23456789123456789123456789m.RoundToSignificantDigits(4)
.Should().Be(1.235m);
1.23456789123456789123456789m.RoundToSignificantDigits(16)
.Should().Be(1.234567891234568m);
1.23456789123456789123456789m.RoundToSignificantDigits(24)
.Should().Be(1.23456789123456789123457m);
1.23456789123456789123456789m.RoundToSignificantDigits(27)
.Should().Be(1.23456789123456789123456789m);
}
Ich fand dieser Artikel tun eine schnelle Suche auf ihn. Im Grunde ist dies eine umwandelt in eine Zeichenfolge und geht durch die Zeichen in diesem Array einen nach dem anderen, bis sie den max erreicht. Bedeutung. Wird diese Arbeit?
Der folgende Code entspricht nicht ganz die Spezifikation, da es nicht abzurunden nicht versuchen, etwas links von dem Komma. Aber es ist einfacher als alles andere hier vorgestellten (bisher). Ich war ziemlich überrascht, dass C # nicht über eine integrierte Methode, dies zu umgehen.
static public string SignificantDigits(double d, int digits=10)
{
int magnitude = (d == 0.0) ? 0 : (int)Math.Floor(Math.Log10(Math.Abs(d))) + 1;
digits -= magnitude;
if (digits < 0)
digits = 0;
string fmt = "f" + digits.ToString();
return d.ToString(fmt);
}
Wie ich es „erhebliche Zahlen“ erinnern bedeutet, die Anzahl der Ziffern nach dem Punkt Separator so 3 signifikante Stellen für 0,012345 0.012 wären und nicht 0,0123, aber das wirklich spielt keine Rolle für die Lösung. Ich verstehe auch, dass Sie wollen die letzten Ziffern zu einem gewissen Grad „zunichte machen“, wenn die Zahl> 1. Sie schreiben, dass 12345 12300 werden würde, aber ich bin nicht sicher, ob Sie wollen 123456 1230000 oder 123400 werden? Meine Lösung hat die letzte. Statt den Faktor zur Berechnung Sie natürlich ein kleines initialisierten Array machen könnte, wenn man nur ein paar Variationen haben.
private static string FormatToSignificantFigures(decimal number, int amount)
{
if (number > 1)
{
int factor = Factor(amount);
return ((int)(number/factor)*factor).ToString();
}
NumberFormatInfo nfi = new CultureInfo("en-US", false).NumberFormat;
nfi.NumberDecimalDigits = amount;
return(number.ToString("F", nfi));
}
private static int Factor(int x)
{
return DoCalcFactor(10, x-1);
}
private static int DoCalcFactor(int x, int y)
{
if (y == 1) return x;
return 10*DoCalcFactor(x, y - 1);
}
Mit freundlichen Grüßen Carsten
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