Class LLR

This class is used to calculate a simple log likelihood ratio for a matrix of counts over two variables that take discrete values. There is no constructor. All methods are static. Author: Michael Towsey.

Inheritance
Object
LLR
Inherited Members
Namespace: TowseyLibrary
Assembly: TowseyLibrary.dll
Syntax
public static class LLR

Methods

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CalculateLogLikelihoodRatio(Double, Double)

See Wikipedia on LLR -2log(Lambda) = -2LLR = 2log[p(x|B)/p(x|Bo)] = 2log[p(x|B)] - 2log[p(x|Bo)] therefore LLR = log[p(x|Bo)] - log[p(x|B)] where x is the observation. where Bo are the parameters of the null hypothesis where B are the parameters of alternative hypothesis.

Declaration
public static double CalculateLogLikelihoodRatio(double unigramLogScore, double bigramLogScore)
Parameters
Type Name Description
Double unigramLogScore

log likelihood of the null hypothesis.
Double bigramLogScore

log likelihood of the alernative hypothesis.
Returns
Type Description
Double
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CellExpectedValue(Int32[,], Int32, Int32, Int32)

Declaration
public static double CellExpectedValue(int[, ] table, int row, int column, int totalCount)
Parameters
Type Name Description
Int32[,] table
Int32 row
Int32 column
Int32 totalCount
Returns
Type Description
Double
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ChiSquare(Int32[,], Double[,], out Double, out Int32)

Calculates the chi square statistic from a contingency table and the transition frequenices of a Markov Model. See my statistics book for engineers and scientists, Walpole and Myers, p345.

Declaration
public static void ChiSquare(int[, ] contingencyTable, double[, ] expectedRf, out double chi2, out int df)
Parameters
Type Name Description
Int32[,] contingencyTable
Double[,] expectedRf
Double chi2
Int32 df
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ChiSquare_DF1(Double)

Declaration
public static double ChiSquare_DF1(double chi)
Parameters
Type Name Description
Double chi
Returns
Type Description
Double
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ChiSquare_DFn(Double, Int32)

Declaration
public static double ChiSquare_DFn(double chi2, int df)
Parameters
Type Name Description
Double chi2
Int32 df
Returns
Type Description
Double
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ColumnRelativeFrequency(Int32[,], Int32, Int32)

Declaration
public static double ColumnRelativeFrequency(int[, ] table, int column, int totalCount)
Parameters
Type Name Description
Int32[,] table
Int32 column
Int32 totalCount
Returns
Type Description
Double
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GetLLRs(Int32[,])

Declaration
public static double[, ] GetLLRs(int[, ] contingencyTable)
Parameters
Type Name Description
Int32[,] contingencyTable
Returns
Type Description
Double[,]
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RowRelativeFrequency(Int32[,], Int32, Int32)

Declaration
public static double RowRelativeFrequency(int[, ] table, int row, int totalCount)
Parameters
Type Name Description
Int32[,] table
Int32 row
Int32 totalCount
Returns
Type Description
Double
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WriteLogLikelihoodRatioMatrix(Double[,])

Declaration
public static string WriteLogLikelihoodRatioMatrix(double[, ] m)
Parameters
Type Name Description
Double[,] m
Returns
Type Description
String