If we have one image from BSD (The Berkeley Segmentation Dataset and Benchmark) and for this images Ground truth, how to calculate PR?

PR is the ratio of true to false edges and can be calculated by the formula:

PR = True Edges (Edge pixels identified as Edges)/False Edges (Non edge pixels identified as edges) + (Edge pixels identified as Non-Edge pixels)

How to find those arguments in formula?

If we have one image from BSD (The Berkeley Segmentation Dataset and Benchmark) and for this images Ground truth, how to calculate PR?

PR is the ratio of true to false edges, and can be calculated by the formula:

PR = True Edges (Edge pixels identified as Edges)/False Edges (Non edge pixels identified as edges) + (Edge pixels identified as Non-Edge pixels)

How to find those arguments in formula?