AUC metric calculates the area of
This value is ultimately returned as auc, an idempotent operation that computes the area under a discretized curve of precision versus recall values (computed using the aforementioned variables).
Therefore, it should be calculating the area under PR, not ROC. However, it also says:
Approximates the AUC (Area under the curve) of the ROC or PR curves
If it calculate the area under PR, then why it says "Approximate ROC or PR" instead of clearly saying "Approximate PR" only without ROC?
Please help understand what I am missing.