R/conf.mat.R

In liver: "Eating the Liver of Data Science"

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#     Copyright (C) 2020 - 2021  Reza Mohammadi & Kevin Burke                  |
#                                                                              |
#     This file is part of 'liver' package.                                    |
#                                                                              |
#     liver 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; see <https://cran.r-project.org/web/licenses/GPL-3>.|
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#     Maintainer: Reza Mohammadi <a.mohammadi@uva.nl>                          |
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#     Create a Confusion Matrix
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conf.mat = function( pred, actual, cutoff = NULL, reference = NULL, 
                     proportion = FALSE, dnn = c( "Predict", "Actual" ), ... )
{
    if( length( pred ) != length( actual ) )
        stop( "prod & actual must have the same length" )
    
    if( !is.null( cutoff ) )
    {
        if( ( cutoff < 0 ) || ( cutoff > 1 ) ) stop( " The value of 'cutoff' must be between 0 and 1." )
        
        levels = base::levels( as.factor( actual ) )
        if( length( levels )  < 2 ) stop( " 'actual' must have more than two levels." )
        if( length( levels ) != 2 ) stop( " For the case 'cutoff != NULL', 'actual' must have two levels." )
        
        if( levels[ 1 ] == 0 ) levels = c( levels[ 2 ], levels[ 1 ] ) 
        
        if( !is.null( reference ) )
            if( which( levels == reference ) == 2 ) levels = c( levels[ 2 ], levels[ 1 ] ) 

        if( is.null( reference ) )
            cat( paste( c( "Setting levels: reference = \"", levels[ 1 ], "\", case = \"", levels[ 2 ],"\"  \n" ), collapse = "" ) ) 
        
        pred = ifelse( pred >= cutoff, levels[ 1 ], levels[ 2 ] )
        
        pred   = factor( pred  , levels = levels )
        actual = factor( actual, levels = levels )
    }
    
    conf_mat = table( pred, actual, dnn = dnn, ... )
    
    if( proportion == TRUE )
        conf_mat = round( conf_mat / sum( conf_mat ), 3 )
    
    return( conf_mat )
}

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