utils.py

import itertools
import matplotlib.pyplot as plt
import numpy as np

# ------------
# plotting utils
# ------------


def plot_confusion_matrix(cm, class_names):
    """
    Returns a matplotlib figure containing the plotted confusion matrix.

    Args:
       cm (array, shape = [n, n]): a confusion matrix of integer classes
       class_names (array, shape = [n]): String names of the integer classes
    """

    figure = plt.figure(figsize=(10, 10))
    # Normalize the confusion matrix. (optional: changes colors here)
    # cm = np.around(cm.astype('float') / cm.sum(axis=1)[:, np.newaxis], decimals=2)

    plt.imshow(cm, interpolation='nearest', cmap=plt.cm.Blues)
    plt.title("Confusion matrix", fontsize=18)
    plt.colorbar()
    tick_marks = np.arange(len(class_names))
    plt.xticks(tick_marks, class_names)
    plt.yticks(tick_marks, class_names, rotation=90)

    # Normalize the confusion matrix. (optional: changes labels here)
    # cm = np.around(cm.astype('float') / cm.sum(axis=1)[:, np.newaxis], decimals=2)

    # Use white text if squares are dark; otherwise black.
    threshold = cm.max() / 2.

    for i, j in itertools.product(range(cm.shape[0]), range(cm.shape[1])):
        color = "white" if cm[i, j] > threshold else "black"
        plt.text(j, i, cm[i, j], horizontalalignment="center", color=color)

    plt.tight_layout()
    plt.ylabel('True label')
    plt.xlabel('Predicted label')
    return figure