C:/Documents and Settings/Stephen/Desktop/Biostatistics Library and Program/Biostatistics/PairedT-TestGroupsCollection.cs

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using System;
using System.Collections;
using System.Collections.Generic;


namespace StephenAshley.Biostatistics
{
   using NUMBER = Decimal;
   public class PairedT_TestGroupsCollection : T_TestGroupsCollection, IEnumerable
   {
      #region *** fields ***
      private Group grpDifferences;
      #endregion
      #region *** constructors ***
      public PairedT_TestGroupsCollection()
         : base()
      {
         grpDifferences = new Group();
      }

      public PairedT_TestGroupsCollection(List<Group> groups)
         : base(groups)
      {
         if (groupsArray[0].n() != groupsArray[1].n())
            throw new BiostatisticsException("Groups have unequal sizes.");

         if (k() == 2)
         {
            grpDifferences = new Group((Int16)groupsArray[0].n());
            for (Int32 i = 0; i < groupsArray[0].n(); i++)
               grpDifferences.Add(groupsArray[0][i] - groupsArray[1][i]);
         }
      }
      #endregion
      #region ***** methods ******
      public override void Add(Group group)
      {
         if (group == null)
            throw new BiostatisticsException("group is a null reference.");

         // If groupsArray contains no groups, add this one.
         if (groupsArray == null || (k() == 0))
         {
            base.Add(group);
            return;
         }

         // If groupsArray contains one group and the groups are the same size, 
         // add this one and complete grpDifferences.
         if (k() == 1 && groupsArray[0].n() == group.n())
         {
            base.Add(group);
            grpDifferences = new Group((Int16)groupsArray[0].n());
            for (Int32 i = 0; i < groupsArray[0].n(); i++)
               grpDifferences.Add(groupsArray[0][i] - groupsArray[1][i]);

            return;
         }

         // If groupsArray contains one group, and the new group has a different size,
         // throw an exception.
         if (k() == 1 && groupsArray[0].n() != group.n())
         {
            throw new BiostatisticsException(
"Groups in a PairedT_TestGroupsCollection must have an equal number of elements.");
         }

         if (k() > 1)
            throw new BiostatisticsException(
"Addition of a Group would result in a PairedT_TestGroupsCollection with more than 2 Groups.");
      }

      public override void AddRange(List<Group> lstGroups)
      {
         if (lstGroups == null)
            throw new BiostatisticsException("lstGroups is a null reference.");

         if (lstGroups.Count == 0)
            throw new BiostatisticsException("lstGroups contains no Groups.");

         if (lstGroups.Count + k() > 2)
            throw new BiostatisticsException(
"Addition of Groups would result in a PairedT-TestGroupsList with more than 2 Groups.");

         if (lstGroups.Count == 1 && k() == 1)
         {
            this.Add(lstGroups[0]);
            return;
         }

         if (groupsArray == null || k() == 0)
         {
            if (lstGroups[0].n() == lstGroups[1].n())
            {
               base.AddRange(lstGroups);
               grpDifferences = new Group((Int16)groupsArray[0].n());
               for (Int32 i = 0; i < groupsArray[0].n(); i++)
                  grpDifferences.Add(groupsArray[0][i] - groupsArray[1][i]);

               return;
            }
            else
               throw new BiostatisticsException(
"Groups in PairedT-TestGroups Collection must have the same number of elements.");
         }
      }

      public new Int32 DegreesOfFreedom()
      { return n() - 1; }

      public new NUMBER EstimatedPopulationVariance()
      {
         NUMBER decEstimatedPopulationVariance;
         try
         {
            decEstimatedPopulationVariance = SumOfSquaredDeviatesOfDifferences() / (n() - 1);
         }
         catch (Exception e)
         {
            throw new BiostatisticsException(e.Source + ": " + e.Message, e);
         }
         return decEstimatedPopulationVariance;
      }

      public NUMBER EstimatedStandardErrorOfDifferencesOfMeans()
      {
         NUMBER decEstimatedStandardErrorOfDifferencesOfMeans;
         try
         {
            decEstimatedStandardErrorOfDifferencesOfMeans =
               DecMath.Sqrt(EstimatedPopulationVariance() / n());
         }
         catch (Exception e)
         {
            throw new BiostatisticsException(e.Source + ": " + e.Message, e);
         }
         return decEstimatedStandardErrorOfDifferencesOfMeans;
      }

      public NUMBER MeanOfDifferences()
      {
         NUMBER decMeanOfDifferences;
         try
         {
            decMeanOfDifferences = SumOfDifferences() / grpDifferences.n();
         }
         catch (Exception e)
         {
            throw new BiostatisticsException(e.Source + ": " + e.Message, e);
         }
         return decMeanOfDifferences;
      }

      public Int32 n()
      { return grpDifferences.n(); }

      public override NUMBER p()
      { return Distributions.ProbabilityT(t(), DegreesOfFreedom()); }

      public NUMBER SumOfDifferences()
      {
         NUMBER decSumOfDifferences = 0.0m;

         foreach (NUMBER value in grpDifferences)
            decSumOfDifferences += value;

         return decSumOfDifferences;
      }

      public NUMBER SumOfSquaredDeviatesOfDifferences()
      {
         return grpDifferences.SumOfSquaredDeviates();
      }

      public override NUMBER t()
      {
         NUMBER decT;
         try
         {
            decT = MeanOfDifferences() / EstimatedStandardErrorOfDifferencesOfMeans();
         }
         catch (Exception e)
         {
            throw new BiostatisticsException(e.Source + ": " + e.Message, e);
         }
         return decT;
      }
      #endregion
   }
}

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