# Confusion matrix

A confusion matrix is a table that is used to evaluate the performance of a classification model. The table shows the predicted classifications for a set of test data compared to the actual classifications. The columns of the table represent the predicted classes and the rows represent the actual classes.

The first step in creating a confusion matrix is to create a set of predictions for the test data. This can be done using a classification model that has been trained on the training data. The predictions can then be compared to the actual classifications of the test data to create the confusion matrix.

The accuracy of the classification model can be calculated from the confusion matrix. The accuracy is the number of correct predictions divided by the total number of predictions.

The confusion matrix can also be used to calculate other measures of performance, such as precision and recall. Precision is the number of correct predictions divided by the total number of predictions. Recall is the number of correct predictions divided by the total number of actual classifications.

The confusion matrix can be a useful tool for evaluating the performance of a classification model. It can be used to calculate accuracy, precision, and recall. It can also be used to compare different classification models.

##### What is confusion matrix with example?

A confusion matrix is a table that is used to evaluate the performance of a machine learning model. The table is made up of four columns: true positives, false positives, true negatives, and false negatives. Each row represents a different class and each column represents a different prediction.

For example, let's say we have a model that is trying to predict whether or not a person will have a heart attack. We would have two classes: those who have a heart attack (positive) and those who do not have a heart attack (negative).

If our model predicts that a person will have a heart attack and they actually do have a heart attack, that is a true positive. If our model predicts that a person will have a heart attack and they actually do not have a heart attack, that is a false positive. If our model predicts that a person will not have a heart attack and they actually do not have a heart attack, that is a true negative. If our model predicts that a person will not have a heart attack and they actually do have a heart attack, that is a false negative.

A confusion matrix can be used to calculate a variety of metrics, such as accuracy, precision, recall, and specificity.

Here is an example confusion matrix:

| | Actual Positive | Actual Negative |
|:-------------:|:---------------:|:---------------:|
|
Predicted Positive
| True

#### What does confusion matrix measure?

A confusion matrix is a table that is used to evaluate the performance of a machine learning model. The table is made up of four different cells, each of which represents a different combination of predicted and actual values. The four cells are as follows:

True Positives: This is the number of times that the model predicted the correct value.

True Negatives: This is the number of times that the model predicted the incorrect value.

False Positives: This is the number of times that the model predicted the correct value, but the actual value was different.

False Negatives: This is the number of times that the model predicted the incorrect value, but the actual value was different.

The confusion matrix can be used to calculate a number of different metrics, such as accuracy, precision, recall, and specificity.

#### What is confusion matrix formula?

A confusion matrix is a table that is used to evaluate the performance of a machine learning model. The matrix is made up of four quadrants:

True positives (TP): These are the cases where the model predicted the correct label and the prediction was correct.

True negatives (TN): These are the cases where the model predicted the correct label and the prediction was incorrect.

False positives (FP): These are the cases where the model predicted the incorrect label and the prediction was correct.

False negatives (FN): These are the cases where the model predicted the incorrect label and the prediction was incorrect.

The formula for the confusion matrix is:

(TP + TN) / (TP + TN + FP + FN)