C:/Documents and Settings/Stephen/Desktop/Biostatistics Library and Program/Biostatistics/DecMath.cs

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using System;
using System.Collections.Generic;


namespace StephenAshley.Biostatistics
{
   public sealed class DecMath
   {
      private DecMath() { }

      public const Decimal PI = 3.1415926535897932384626433833m;

      public const Decimal e = 2.71828182845904523536028747m;

      public static Decimal Abs(Decimal value)
      {
         if (value < 0m)
            return -1.0m * value;
         else return value;
      }

      public static Decimal Atan(Decimal angle)
      {
         return new Decimal(Math.Atan(Decimal.ToDouble(angle)));
      }

      public static Decimal Cos(Decimal angle)
      {
         return new Decimal(Math.Cos(Decimal.ToDouble(angle)));
      }

      // TODO Replace the Double computation with a Decimal computation.
      public static Decimal Exp(Decimal value)
      {
         return new Decimal(Math.Exp(Decimal.ToDouble(value)));
      }

      public static double Factorial(Int32 value)
      {
         //if (value == 0.0m) return 1.0m;
         //return value * Factorial(value - 1.0m);

         double Result = (double)value;

         for (Int32 i = value - 1; i > 0; i--)
            Result *= (double) i;
         return Result;
      }

      public static Decimal Pow(Decimal value, Int32 power)
      {
         if (power < 1)
            throw new ArgumentException("power must be greater than 1.", "power");
         Decimal A = 1.0m;
         for (Int32 i = power; i > 0; i--)
            A = A * value;
         return A;
      }

      public static Decimal Pow(Decimal value, Int64 power)
      {
         if (power < 1)
            throw new ArgumentException("power must be greater than 1.", "power");
         Decimal A = 1.0m;
         for (Int64 i = power; i > 0; i--)
            A = A * value;
         return A;
      }

      //NUMBER factorial(NUMBER factor_me)
      //{
      //   if (factor_me == 0.0m) return 1.0m;
      //   return factor_me * factorial(factor_me - 1.0m);
      //}

      public static bool IsDecimal(string value)
      {
         try
         {
            Decimal decTemp = Convert.ToDecimal(value);
         }
         catch (FormatException)
         {
            return false;
         }
         catch (OverflowException)
         {
            throw;
         }
         return true;
      }

      //public static bool IsEven(Decimal value)
      //{
      //   if (Decimal.Remainder(value, 2m) == 0m)
      //      return true;
      //   else return false;
      //}

      public static bool IsEven(Int32 value)
      {
         Int32 result;
         Math.DivRem(value, 2, out result);
         if (result == 0)
            return true;
         else return false;
      }

      //public static bool IsOdd(Decimal value)
      //{
      //   if (Decimal.Remainder(value, 2m) != 0m)
      //      return true;
      //   else return false;
      //}

      public static bool IsOdd(Int32 value)
      {
         Int32 result;
         Math.DivRem(value, 2, out result);
         if (result != 0)
            return true;
         else return false;
      }

      public static Decimal Log(Decimal value)
      {
         return new Decimal(Math.Log(Decimal.ToDouble(value)));
      }
      // TODO Replace the Double computation with a Decimal computation.
      public static Decimal Log10(Decimal value)
      {
         return new Decimal(Math.Log10(Decimal.ToDouble(value)));
      }

      public static Decimal Sin(Decimal angle)
      {
         return new Decimal(Math.Sin(Decimal.ToDouble(angle)));
      }

      public static Decimal Sqrt(Decimal value)
      {
         if (value == 1m)
            return 1m;

         if (value == 0m)
            return 0m;

         if (value < 0m)
            throw new ArgumentException(
               "Argument to Sqrt method must be greater than or equal to 0.");

         Decimal decGuess = (Decimal)(Math.Sqrt(Decimal.ToDouble(value)));
         Decimal decTooBig;
         Decimal decTooSmall;
         if (value > 1m)
         {
            decTooBig = value;
            decTooSmall = 1m;
         }
         else
         {
            decTooBig = 1m;
            decTooSmall = 0m;
         }
         return SquareRoot(value, decTooSmall, decTooBig,
            decGuess);
      }

      private static Decimal SquareRoot(Decimal decSubject,
         Decimal decLowEnd, Decimal decHighEnd, Decimal decNextGuess)
      {
         Int32 iCount = 0;
         while (iCount < 1000)
         {
            checked
            {
               Decimal decTrial = decNextGuess * decNextGuess;

               if (decTrial == decSubject)
                  return decNextGuess;
               else if (decTrial > decSubject)
                  decHighEnd = decNextGuess;
               else
                  decLowEnd = decNextGuess;

               decNextGuess = (decLowEnd + decHighEnd) / 2m;
               iCount++;
            }
         }
         return decNextGuess;
      }

      public static Decimal KahanSum(Decimal[] values)
      {
         if (values.Length == 0)
            return 0m;
         Decimal decSum = values[0];
         Decimal decCorrection = 0m;
         Decimal decCorrectedNextTerm,
                 decNewSum;

         for (Int32 i = 1; i < values.Length; i++)
         {
            decCorrectedNextTerm = values[i] - decCorrection;
            decNewSum = decSum + decCorrectedNextTerm;
            decCorrection = decNewSum - decSum;
            decCorrection = decCorrection - decCorrectedNextTerm;
            decSum = decNewSum;
         }
         return decSum;
      }

      public static Decimal KahanSum(List<Decimal> values)
      {
         return KahanSum(values.ToArray());
      }
   }
}

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