Confusion Matrix is an important tool used in machine learning to evaluate the accuracy of a classification model. It is a table that is used to describe the performance of a classification model on a set of test data for which the true values are known.
A confusion matrix is a table that is often used to describe the performance of a classification model on a set of test data for which the true values are known. It allows the visualization of the performance of an algorithm. Each row of the matrix represents the instances in a predicted class while each column represents the instances in an actual class (or vice versa). The name stems from the fact that it makes it easy to see if the system is confusing two classes (i.e. commonly mislabeling one as another).
The basic entry of the confusion matrix is the number of correctly and incorrectly classified instances, with the corresponding row and column labels. The diagonal elements represent the number of points for which the predicted label is equal to the true label, while off-diagonal elements are those that are mislabeled by the classifier. The support is the number of actual occurrences of the class in the test set.
The confusion matrix can be used to calculate a variety of metrics, such as accuracy, precision, recall, and the F1 score. Accuracy is the ratio of correctly predicted observation to the total observations. Precision is the ratio of correctly predicted positive observations to the total predicted positive observations. Recall is the ratio of correctly predicted positive observations to the all observations in actual class – yes. The F1 score is the weighted average of precision and recall.
The confusion matrix is an important tool for machine learning practitioners as it provides insight into the performance of their model. It is also useful for comparing different models and for selecting the best one for a given task.