python-scikit-learnR2 score for linear regression

Usage example

import numpy as np
from sklearn import datasets, linear_model, model_selection, metrics

X, y = datasets.load_diabetes(return_X_y=True)
X_train, X_test, y_train, y_test = model_selection.train_test_split(X, y)

model = linear_model.LinearRegression()
model.fit(X_train, y_train)
r2 = model.score(X_test, y_test)

print(r2)

output

0.5278235386853034