Wartość RMSE z walidacji krzyżowej

# Perform cross-validation
scores = cross_val_score(model, X, y, cv=kf, scoring="neg_mean_squared_error")

# Calculate RMSE
rmse = np.sqrt(-scores)
print("Average RMSE: {}".format(np.mean(rmse)))
print("Standard Deviation of the target array: {}".format(np.std(y)))
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