How to find the Precision, Recall, Accuracy using SVM?

Question

Duplicate calculating Precision, Recall and F Score

I have a input file with text description and classified level (i.e.levelA and levelB). I want to write a SVM classifier that measure precision, recall and accuracy. I looked at scikit and LIBSVM but I want to know more step by step.

Any sample code or basic tutorial would be really nice. Thanks for any suggestion in advance.

Solution

These performance measures are easy to obtain from the predicted labels and true labels, as a post-processing step:

1. Precision = TP / (TP+FP)
2. Recall = TP / (TP+FN)
3. Accuracy = (TP + TN) / (TP + TN + FP + FN)

With TP, FP, TN, FN being number of true positives, false positives, true negatives and false negatives, respectively.