Fix confusion_matrix crash on single-class predictions#85
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When all labels or predictions are the same class, sklearn's confusion_matrix returns a 1x1 matrix. Unpacking into 4 variables crashes with ValueError. Fix: Pass labels=[0, 1] to force 2x2 matrix, handle empty input, and guard average_precision_score against single-class y_true. Example: y_true = [0, 0, 0, 0], y_pred = [0.1, 0.2, 0.1, 0.3] Before: confusion_matrix -> [[4]] -> ValueError on unpack After: confusion_matrix(labels=[0,1]) -> [[4,0],[0,0]] -> works
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When all labels or predictions are the same class, sklearn's confusion_matrix returns a 1x1 matrix. Unpacking into 4 variables crashes with ValueError.
Fix: Pass labels=[0, 1] to force 2x2 matrix, handle empty input, and guard average_precision_score against single-class y_true.
Example:
y_true = [0, 0, 0, 0], y_pred = [0.1, 0.2, 0.1, 0.3]
Before: confusion_matrix -> [[4]] -> ValueError on unpack
After: confusion_matrix(labels=[0,1]) -> [[4,0],[0,0]] -> works