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Pretty print a confusion matrix with seaborn
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import pandas as pd | |
import matplotlib.pyplot as plt | |
import seaborn as sns | |
def print_confusion_matrix(confusion_matrix, class_names, figsize = (10,7), fontsize=14): | |
"""Prints a confusion matrix, as returned by sklearn.metrics.confusion_matrix, as a heatmap. | |
Note that due to returning the created figure object, when this funciton is called in a | |
notebook the figure willl be printed twice. To prevent this, either append ; to your | |
function call, or modify the function by commenting out the return expression. | |
Arguments | |
--------- | |
confusion_matrix: numpy.ndarray | |
The numpy.ndarray object returned from a call to sklearn.metrics.confusion_matrix. | |
Similarly constructed ndarrays can also be used. | |
class_names: list | |
An ordered list of class names, in the order they index the given confusion matrix. | |
figsize: tuple | |
A 2-long tuple, the first value determining the horizontal size of the ouputted figure, | |
the second determining the vertical size. Defaults to (10,7). | |
fontsize: int | |
Font size for axes labels. Defaults to 14. | |
Returns | |
------- | |
matplotlib.figure.Figure | |
The resulting confusion matrix figure | |
""" | |
df_cm = pd.DataFrame( | |
confusion_matrix, index=class_names, columns=class_names, | |
) | |
fig = plt.figure(figsize=figsize) | |
try: | |
heatmap = sns.heatmap(df_cm, annot=True, fmt="d") | |
except ValueError: | |
raise ValueError("Confusion matrix values must be integers.") | |
heatmap.yaxis.set_ticklabels(heatmap.yaxis.get_ticklabels(), rotation=0, ha='right', fontsize=fontsize) | |
heatmap.xaxis.set_ticklabels(heatmap.xaxis.get_ticklabels(), rotation=45, ha='right', fontsize=fontsize) | |
plt.ylabel('True label') | |
plt.xlabel('Predicted label') | |
# Note that due to returning the created figure object, when this funciton is called in a notebook | |
# the figure willl be printed twice. To prevent this, either append ; to your function call, or | |
# modify the function by commenting out this return expression. | |
return fig |
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