Create a Confusion Matrix in R
A confusion matrix is a tabular representation of Actual vs Predicted values.
As you can see, the confusion matrix avoids "confusion" by measuring the actual and predicted values in a tabular format. In table above, Positive class = 1 and Negative class = 0. Following are the metrics we can derive from a confusion matrix:
Accuracy - It determines the overall predicted accuracy of the model. It is calculated as Accuracy = (True Positives + True Negatives)/(True Positives + True Negatives + False Positives + False Negatives)
True Positive Rate (TPR) - It indicates how many positive values, out of all the positive values, have been correctly predicted. The formula to calculate the true positive rate is (TP/TP + FN). Also, TPR = 1 - False Negative Rate. It is also known as Sensitivity or Recall.
False Positive Rate (FPR) - It indicates how many negative values, out of all the negative values, have been incorrectly predicted. The formula to calculate the false positive rate is (FP/FP + TN). Also, FPR = 1 - True Negative Rate.
True Negative Rate (TNR) - It indicates how many negative values, out of all the negative values, have been correctly predicted. The formula to calculate the true negative rate is (TN/TN + FP). It is also known as Specificity.
False Negative Rate (FNR) - It indicates how many positive values, out of all the positive values, have been incorrectly predicted. The formula to calculate false negative rate is (FN/FN + TP).
Precision: It indicates how many values, out of all the predicted positive values, are actually positive. It is formulated as:(TP / TP + FP).
F Score: F score is the harmonic mean of precision and recall. It lies between 0 and 1. Higher the value, better the model. It is formulated as 2((precision*recall) / (precision+recall)).
We can create the confusion matrix for our data.
> confusionMatrix(credit_test$Creditability,pred_value_labels) Confusion Matrix and Statistics Reference Prediction 0 1 0 48 32 1 59 161 Accuracy : 0.6967 95% CI : (0.6412, 0.7482) No Information Rate : 0.6433 P-Value [Acc > NIR] : 0.02975 Kappa : 0.2996 Mcnemar's Test P-Value : 0.00642 Sensitivity : 0.4486 Specificity : 0.8342 Pos Pred Value : 0.6000 Neg Pred Value : 0.7318 Prevalence : 0.3567 Detection Rate : 0.1600 Detection Prevalence : 0.2667 Balanced Accuracy : 0.6414 'Positive' Class : 0
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