Confusion matrix as a table

Source: R/confusionMatrix.R

Conversion functions for class confusionMatrix

# S3 method for confusionMatrix
as.matrix(x, what = "xtabs", ...)

Arguments

x

an object of class confusionMatrix
what

data to convert to matrix. Either "xtabs", "overall" or "classes"
...

not currently used

Value

A matrix or table

Details

For as.table, the cross-tabulations are saved. For as.matrix, the three object types are saved in matrix format.

Examples

###################
## 2 class example

lvs <- c("normal", "abnormal")
truth <- factor(rep(lvs, times = c(86, 258)),
                levels = rev(lvs))
pred <- factor(
               c(
                 rep(lvs, times = c(54, 32)),
                 rep(lvs, times = c(27, 231))),
               levels = rev(lvs))

xtab <- table(pred, truth)

results <- confusionMatrix(xtab)
as.table(results)
#>           truth
#> pred       abnormal normal
#>   abnormal      231     32
#>   normal         27     54
as.matrix(results)
#>          abnormal normal
#> abnormal      231     32
#> normal         27     54
as.matrix(results, what = "overall")
#>                        [,1]
#> Accuracy       0.8284883721
#> Kappa          0.5335968379
#> AccuracyLower  0.7844134380
#> AccuracyUpper  0.8667985207
#> AccuracyNull   0.7500000000
#> AccuracyPValue 0.0003096983
#> McnemarPValue  0.6025370061
as.matrix(results, what = "classes")
#>                           [,1]
#> Sensitivity          0.8953488
#> Specificity          0.6279070
#> Pos Pred Value       0.8783270
#> Neg Pred Value       0.6666667
#> Precision            0.8783270
#> Recall               0.8953488
#> F1                   0.8867562
#> Prevalence           0.7500000
#> Detection Rate       0.6715116
#> Detection Prevalence 0.7645349
#> Balanced Accuracy    0.7616279

###################
## 3 class example

xtab <- confusionMatrix(iris$Species, sample(iris$Species))
as.matrix(xtab)
#>            setosa versicolor virginica
#> setosa         17         16        17
#> versicolor     16         18        16
#> virginica      17         16        17