Why is my ROC curve inverted in R?
When the ROC curve dips prominently into the lower right half of the graph, this is likely a sign that either the wrong State Value has been specified or the wrong Test-State association direction has been specified in the “Test Direction” area of the “ROC Curve:Options” dialog.
Can ROC curve be concave?
If the ROC curve is concave then clearly the function R is concave as well, and so its derivative R (p) is nonincreasing in p ∈ (0,1). However, the slope R (p) equals the likelihood ratio LR(x) at a certain value x that decreases with p, which establishes the equivalence of (a) and (b).
Is the ROC curve under the diagonal line?
In the graph that was produced, the ROC curve is below the diagonal reference line, projecting into the lower right half of the graph. The Area Under the Curve (AUC) is .260 and significantly different from .5.
Which is a better classifier for a ROC curve?
Classifiers that give curves closer to the top-left corner indicate a better performance. As a baseline, a random classifier is expected to give points lying along the diagonal (FPR = TPR). The closer the curve comes to the 45-degree diagonal of the ROC space, the less accurate the test.
How are ROC curves used in the real world?
In addition the area under the ROC curve gives an idea about the benefit of using the test (s) in question. ROC curves are used in clinical biochemistry to choose the most appropriate cut-off for a test. The best cut-off has the highest true positive rate together with the lowest false positive rate.
What does it mean when the ROC curve dips?
When the ROC curve dips prominently into the lower right half of the graph, this is likely a sign that either the wrong State Value has been specified or the wrong Test-State association direction has been specified in the “Test Direction” area of the “ROC Curve:Options” dialog.