NMath Stats User's Guide

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8.5 Two-Way Repeated Measures ANOVA (.NET, C#, CSharp, VB, Visual Basic, F#)

NMath Stats provides two classes for calculating a two-way analysis of variance with repeated measures (RANOVA):

Class TwoWayRanova performs a balanced two-way analysis of variance with repeated measures on one factor.

Class TwoWayRanovaTwo performs a balanced two-way analysis of variance with repeated measures on both factors.

Both classes extend TwoWayAnova, and so inherit the methods and properties described in Section 8.3. Like TwoWayAnova, both TwoWayRanova and TwoWayRanovaTwo use multiple linear regression to compute the RANOVA values.

Creating Two-Way RANOVA Objects

Instances of both TwoWayRanova and TwoWayRanovaTwo are constructed from data in a data frame. Three column indices are specified in the data frame: the column containing the first factor, the column containing the second factor, and the column containing the numeric data. For TwoWayRanova, the first factor is the repeated factor; for TwoWayRanovaTwo, both factors are repeated.

For example, this code groups the numeric data in column 3 of DataFrame df by factors constructed from columns 0 and 4:

Code Example – C# RANOVA

var ranova = new TwoWayRanova( df, 0, 4, 3 );

The factor constructed from column 0 is the repeated factor. In the following example, both factors are repeated:

Code Example – C# RANOVA

var ranova2 = new TwoWayRanovaTwo( df, 0, 4, 3 );

NOTE—Both TwoWayRanova and TwoWayRanovaTwo throw an InvalidArgumentEx­ception if the data contains missing values (NaNs).

Two-Way RANOVA Tables

Once you've constructed a TwoWayRanova, you can display the complete RANOVA table:

Code Example – C# RANOVA

var ranova = new TwoWayRanova( df, 0, 4, 3 );
Console.WriteLine( ranova );

For instance:

Source  Deg of Freedom  SumOfSqu   Mean Square  F         P
FactorA      1          0.2032     0.2032       29.2322   0.0001
Subjects     14         1.7559     0.1254       .         .
FactorB      1          0.0205     0.0205       0.1635    0.6921
Interaction  1          0.0830     0.0830       11.9442   0.0039
Error        14         0.0973     0.0070       .         .
Total        31         2.1599     .            .         .

Class TwoWayRanovaTable summarizes the information in a traditional two-way RANOVA table with repeated measures on one factor. An instance of TwoWayRanovaTable can be obtained from a TwoWayRanova object using the RanovaTable property. For example:

Code Example – C# RANOVA

TwoWayRanovaTable myTable = ranova.RanovaTable;

Class TwoWayRanovaTable derives from TwoWayAnovaTable, and so inherits the properties described in Section 8.3. In addition, TwoWayRanovaTable provides the following properties for accessing the new row in the RANOVA table for repeated measures on one factor:

SubjectsDegreesOfFreedom gets the subjects degrees of freedom.

SubjectsSumOfSquares gets the sum of squares for the subjects.

SubjectsMeanSquare gets the mean square for the subjects.

Similarly, once you've constructed a TwoWayRanovaTwo, you can display the RANOVA table:

Code Example – C# RANOVA

var ranova2 = new TwoWayRanovaTwo( df, 0, 4, 3 );
Console.WriteLine( ranova2 );

For example:

Source  Deg of Freedom  SumOfSq    Mean Square  F         P
FactorA      1          1.4700     1.4700       88.2000   0.0000
FactorB      2         14.5654     7.2827       59.2348   0.0000
Interaction  2          3.3387     1.6694       18.9305   0.0001
A x Subject  14         1.7213     0.1229       .         .
B x Subject  7          0.1167     0.0167       .         .
Error        14         1.2346     0.0882       .         .
Total        47        29.3592     .            .         .

An instance of TwoWayRanovaTwoTable can be obtained from a TwoWayRanovaTwo object using the RanovaTable property. For example:

Code Example – C# RANOVA

TwoWayRanovaTwoTable myTable = ranova2.RanovaTable;

Class TwoWayRanovaTwoTable also derives from TwoWayAnovaTable, and provides the following methods for accessing the additional rows in the RANOVA table with repeated measures on both factors:

SubjectInteractionDegreesOfFreedom() returns the degrees of freedom for the interaction between subjects and the specified factor.

SubjectInteractionSumOfSquares() returns the sum of squares for the interaction between subjects and the specified factor.

SubjectInteractionMeanSquare returns the mean square for the interaction between subjects and the specified factor.


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