            function updateConfusionMatrix(confusionMatrix, testLabels, predictedLabels, distinct) {

                for (var i = 0; i < predictedLabels.length; i++) {
                    const actualIdx = distinct.indexOf(testLabels[i]);
                    const predictedIdx = distinct.indexOf(predictedLabels[i]);
                    if (actualIdx < 0 || predictedIdx < 0) {
                        // eslint-disable-next-line no-console
                        console.warn(`ignore unknown predicted label ${predictedLabels[i]}`);
                    }
                    confusionMatrix[actualIdx][predictedIdx]++;
                }
            }