calculate precision and recall in a confusion matrix

Question

Suppose I have a confusion matrix as like as below. How can I calculate precision and recall?

Answer 1

I don't think you need summation at last. Without summation, your method is correct; it gives precision and recall for each class.

If you intend to calculate average precision and recall, then you have two options: micro and macro-average.

Read more here http://scikit-learn.org/stable/auto_examples/model_selection/plot_precision_recall.html