# SkopeRules example¶

An example using SkopeRules for imbalanced classification.

SkopeRules find logical rules with high precision and fuse them. Finding good rules is done by fitting classification and regression trees to sub-samples. A fitted tree defines a set of rules (each tree node defines a rule); rules are then tested out of the bag, and the ones with higher precision are selected and merged. This produces a real-valued decision function, reflecting for each new sample how many rules (each weighted by respective precision) have found it abnormal.

```import numpy as np
import matplotlib.pyplot as plt
from skrules import SkopeRules
print(__doc__)

rng = np.random.RandomState(42)

n_inliers = 1000
n_outliers = 50

# Generate train data
I = 0.5 * rng.randn(int(n_inliers / 2), 2)
X_inliers = np.r_[I + 2, I - 2]
O = 0.5 * rng.randn(n_outliers, 2)
X_outliers = O  # np.r_[O, O + [2, -2]]
X_train = np.r_[X_inliers, X_outliers]
y_train =  * n_inliers +  * n_outliers
```

## Training the SkopeRules classifier¶

```# fit the model
clf = SkopeRules(random_state=rng, n_estimators=10)
clf.fit(X_train, y_train)

# plot the line, the samples, and the nearest vectors to the plane
xx, yy = np.meshgrid(np.linspace(-5, 5, 50), np.linspace(-5, 5, 50))
Z = clf.decision_function(np.c_[xx.ravel(), yy.ravel()])
Z = Z.reshape(xx.shape)

plt.title("Skope Rules, value of the decision_function method")
plt.contourf(xx, yy, Z, cmap=plt.cm.Blues)

a = plt.scatter(X_inliers[:, 0], X_inliers[:, 1], c='white',
s=20, edgecolor='k')
b = plt.scatter(X_outliers[:, 0], X_outliers[:, 1], c='red',
s=20, edgecolor='k')
plt.axis('tight')
plt.xlim((-5, 5))
plt.ylim((-5, 5))
plt.legend([a, b],
["inliers", "outliers"],
loc="upper left")
plt.show()
``` ## Extracting top rules¶

On the 4 following figures, the predict_top_rules method is used with several values of n_rules. n_rules = 2 means that the prediction is done using only the 2 best rules.

```print('The 4 most precise rules are the following:')
for rule in clf.rules_[:4]:
print(rule)

fig, axes = plt.subplots(2, 2, figsize=(12, 5),
sharex=True, sharey=True)
for i_ax, ax in enumerate(np.ravel(axes)):
Z = clf.predict_top_rules(np.c_[xx.ravel(), yy.ravel()], i_ax+1)
Z = Z.reshape(xx.shape)
ax.set_title("Prediction with predict_top_rules, n_rules="+str(i_ax+1))
ax.contourf(xx, yy, Z, cmap=plt.cm.Blues)

a = ax.scatter(X_inliers[:, 0], X_inliers[:, 1], c='white',
s=20, edgecolor='k')
b = ax.scatter(X_outliers[:, 0], X_outliers[:, 1], c='red',
s=20, edgecolor='k')
ax.axis('tight')
plt.xlim((-5, 5))
plt.ylim((-5, 5))
plt.legend([a, b],
["inliers", "outliers"],
loc="upper left")
plt.show()
``` Out:

```The 4 most precise rules are the following:
c0 <= 1.15681171417 and c0 > -0.680330395699 and c1 <= 1.08434700966
c0 > -0.841694712639 and c1 <= 0.687212407589 and c1 > -1.21965646744
c0 <= 1.03912234306 and c0 > -0.663101434708 and c1 <= 1.27947068214
c0 > -0.841694712639 and c1 <= 0.687212407589 and c1 > -1.43224191666
```

Total running time of the script: ( 0 minutes 2.135 seconds)

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