How to Visualize a Decision Tree from a Random Forest in Python using Scikit-Learn

How to Visualize a Decision Tree from a Random Forest in Python using Scikit-LearnA helpful utility for understanding your modelWill KoehrsenBlockedUnblockFollowFollowingAug 18, 2018Here’s the complete code: just copy and paste into a Jupyter Notebook or Python script, replace with your data and run:Code to visualize a decision tree and save as png (on GitHub here).

The final result is a complete decision tree as an image.

Decision Tree for Iris DatasetExplanation of codeCreate a model train and extract: we could use a single decision tree, but since I often employ the random forest for modeling it’s used in this example.

(The trees will be slightly different from one another!).

from sklearn.

ensemble import RandomForestClassifiermodel = RandomForestClassifier(n_estimators=10)# Trainmodel.


data, iris.

target)# Extract single treeestimator = model.


Export Tree as .

dot File: This makes use of the export_graphviz function in Scikit-Learn.

There are many parameters here that control the look and information displayed.

Take a look at the documentation for specifics.

from sklearn.

tree import export_graphviz# Export as dot fileexport_graphviz(estimator_limited, out_file='tree.

dot', feature_names = iris.

feature_names, class_names = iris.

target_names, rounded = True, proportion = False, precision = 2, filled = True)3.

Convert dot to png using a system command: running system commands in Python can be handy for carrying out simple tasks.

This requires installation of graphviz which includes the dot utility.

For the complete options for conversion, take a look at the documentation.

# Convert to pngfrom subprocess import callcall(['dot', '-Tpng', 'tree.

dot', '-o', 'tree.

png', '-Gdpi=600'])4.

Visualize: the best visualizations appear in the Jupyter Notebook.

(Equivalently you can use matplotlib to show images).

# Display in jupyter notebookfrom IPython.

display import ImageImage(filename = 'tree.

png')ConsiderationsWith a random forest, every tree will be built differently.

I use these images to display the reasoning behind a decision tree (and subsequently a random forest) rather than for specific details.

It’s helpful to limit maximum depth in your trees when you have a lot of features.

Otherwise, you end up with massive trees, which look impressive, but cannot be interpreted at all!.Here’s a full example with 50 features.

Full decision tree from a real problem (see here).

ConclusionsMachine learning still suffers from a black box problem, and one image is not going to solve the issue!.Nonetheless, looking at an individual decision tree shows us this model (and a random forest) is not an unexplainable method, but a sequence of logical questions and answers — much as we would form when making predictions.

Feel free to use and adapt this code for your data.

As always, I welcome feedback, constructive criticism, and hearing about your data science projects.

I can be reached on Twitter @koehrsen_will.

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