ValueError: Only one class present in y_true. ROC AUC score is not defined in that case
I want to calculate AUROC using dataset with all instance zero. However, the following error occurred:

ValueError: Only one class present in y_true. ROC AUC score is not defined in that case

def computeAUROC (dataGT, dataPRED, classCount):

    outAUROC = []

    datanpGT = dataGT.cpu().numpy()
    datanpPRED = dataPRED.cpu().numpy()

    for i in range(classCount):
        outAUROC.append(roc_auc_score(datanpGT[:, i], datanpPRED[:, i]))

    return outAUROC


You cannot have an ROC curve without both positive and negative examples in your dataset. With only one class in the dataset, you cannot measure your false-positive rate, and therefore cannot plot an ROC curve. This is why you get this error message.
