Equations · Machine learning
F1 score
One number that balances precision and recall: their harmonic mean.
F₁ = 2PR / (P + R)
Aethel says
F sub one equals 2 P R over the quantity P plus R
What it says
Precision P is the share of positive predictions that were right; recall R is the share of actual positives that were found. The F1 score is high only when both are high.
Because it ignores true negatives, it suits problems where the positive class is rare.
Symbol by symbol
| Symbol | Say it | Means |
|---|---|---|
| F₁ | F sub one, or F one | the F1 score |
| P | P | precision |
| R | R | recall |
Where you meet it
Evaluating classifiers, search and information retrieval.
Questions
How do you say F1 score out loud?
F₁ = 2PR / (P + R) is read: “F sub one equals 2 P R over the quantity P plus R.” That is exactly what Aethel says when it meets the formula in a book.
What does F₁ mean in F1 score?
F₁ (said “F sub one, or F one”) is the F1 score.
What does P mean in F1 score?
P (said “P”) is precision.
Can I listen to the equations in my own textbook like this?
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