F1-Score or F-measure is an evaluation metric for a classification defined as the harmonic mean of precision and recall. It is a statistical measure of the accuracy of a test or model. Mathematically, it is expressed as follows,
Here, the value of F-measure(F1-score) reaches the best value at 1 and the worst value at 0. F1-score 1 represents the perfect accuracy and recall of the model.
Now let’s see what Recall and precision actually means,
Recall: It tells us what proportion of Data belonging to a certain class say, class A is classified correctly as in class A by our classifier.
Precision: It tells us what proportion of data that our classifier has classified in a certain class, say class A actually belongs to the same class A.
To understand more about precision and recall with a mathematical example, you can visit here.
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What is the importance of the F1 score?
F1-Score (F-measure) is an evaluation metric, that is used to express the performance of the machine learning model (or classifier). It gives the combined information about the precision and recall of a model. This means a high F1-score indicates a high value for both recall and precision. Generally, F1-score is used when we need to compare two or more machine learning algorithms for the same data. We opt for the algorithm whose f1 score is higher.