Python for Data Science Cheat Sheet Scikit-Learn

Python For Data Science Cheat Sheet Create Your Model Evaluate Your Model’s Performance Scikit-Learn Supervised Learning Estimators Classification Metrics Learn Python for data science Interactively at www.DataCamp.com Linear Regression Accuracy Score Estimator score method >>> from sklearn.linear_model import LinearRegression >>> knn.score(X_test, y_test) >>> lr = LinearRegression(normalize=True) >>> from sklearn.metrics import accuracy_score Metric scoring functions Support Vector Machines (SVM) >>> accuracy_score(y_test, y_pred) Scikit-learn >>> from sklearn.svm import SVC Classification Report >>> svc = SVC(kernel='linear') >>> from sklearn.metrics import classification_report Precision, recall, f1-score Scikit-learn is an open source Python library that Naive Bayes >>> print(classification_report(y_test, y_pred)) and support implements a range of machine learning, Confusion Matrix >>> from sklearn.naive_bayes import GaussianNB preprocessing, cross-validation and visualization >>> from sklearn.metrics import confusion_matrix >>> gnb = GaussianNB() >>> print(confusion_matrix(y_test, y_pred)) algorithms using a unified interface. KNN Regression Metrics A Basic Example >>> from sklearn import neighbors >>> knn = neighbors.KNeighborsClassifier(n_neighbors=5) Mean Absolute Error >>> from sklearn import neighbors, datasets, preprocessing Unsupervised Learning Estimators >>> from sklearn.model_selection import train_test_split >>> from sklearn.metrics import mean_absolute_error >>> from sklearn.metrics import accuracy_score >>> y_true = [3, -0.5, 2] >>> iris = datasets.load_iris() Principal Component Analysis (PCA) >>> mean_absolute_error(y_true, y_pred) >>> X, y = iris.data[:, :2], iris.target >>> from sklearn.decomposition import PCA Mean Squared Error >>> X_train, X_test, y_train, y_test = train_test_split(X, y, random_state=33) >>> pca = PCA(n_components=0.95) >>> from sklearn.metrics import mean_squared_error >>> scaler = preprocessing.StandardScaler().fit(X_train) K Means >>> mean_squared_error(y_test, y_pred) >>> X_train = scaler.transform(X_train) R² Score >>> X_test = scaler.transform(X_test) >>> from sklearn.cluster import KMeans >>> knn = neighbors.KNeighborsClassifier(n_neighbors=5) >>> k_means = KMeans(n_clusters=3, random_state=0) >>> from sklearn.metrics import r2_score >>> knn.fit(X_train, y_train) >>> r2_score(y_true, y_pred) >>> y_pred = knn.predict(X_test) Clustering Metrics >>> accuracy_score(y_test, y_pred) Model Fitting Adjusted Rand Index Supervised learning Also see NumPy & Pandas Fit the model to the data >>> from sklearn.metrics import adjusted_rand_score Loading The Data >>> lr.fit(X, y) >>> adjusted_rand_score(y_true, y_pred) >>> knn.fit(X_train, y_train) Your data needs to be numeric and stored as NumPy arrays or SciPy sparse >>> svc.fit(X_train, y_train) Homogeneity matrices. Other types that are convertible to numeric arrays, such as Pandas Unsupervised Learning >>> from sklearn.metrics import homogeneity_score Fit the model to the data >>> homogeneity_score(y_true, y_pred) DataFrame, are also acceptable. >>> k_means.fit(X_train) V-measure >>> pca_model = pca.fit_transform(X_train) Fit to data, then transform it >>> import numpy as np >>> from sklearn.metrics import v_measure_score >>> X = np.random.random((10,5)) >>> metrics.v_measure_score(y_true, y_pred) >>> y = np.array(['M','M','F','F','M','F','M','M','F','F','F']) >>> X[X < 0.7] = 0 Prediction Cross-Validation Supervised Estimators >>> from sklearn.cross_validation import cross_val_score Predict labels >>> print(cross_val_score(knn, X_train, y_train, cv=4)) Training And Test Data >>> y_pred = svc.predict(np.random.random((2,5))) >>> print(cross_val_score(lr, X, y, cv=2)) >>> y_pred = lr.predict(X_test) Predict labels >>> from sklearn.model_selection import train_test_split >>> y_pred = knn.predict_proba(X_test) Estimate probability of a label > > > X_train, X_test, y_train, y_test = train_test_split(X , Unsupervised Estimators Tune Your Model y, Predict labels in clustering algos random_state=0) >>> y_pred = k_means.predict(X_test) Grid Search >>> from sklearn.grid_search import GridSearchCV >>> params = {"n_neighbors": np.arange(1,3), Preprocessing The Data "metric": ["euclidean", "cityblock"]} >>> grid = GridSearchCV(estimator=knn, Standardization Encoding Categorical Features param_grid=params) >>> grid.fit(X_train, y_train) >>> from sklearn.preprocessing import StandardScaler >>> from sklearn.preprocessing import LabelEncoder >>> print(grid.best_score_) >>> print(grid.best_estimator_.n_neighbors) >>> scaler = StandardScaler().fit(X_train) >>> enc = LabelEncoder() >>> standardized_X = scaler.transform(X_train) >>> y = enc.fit_transform(y) >>> standardized_X_test = scaler.transform(X_test) Randomized Parameter Optimization Normalization Imputing Missing Values >>> from sklearn.grid_search import RandomizedSearchCV >>> params = {"n_neighbors": range(1,5), >>> from sklearn.preprocessing import Normalizer "weights": ["uniform", "distance"]} >>> from sklearn.preprocessing import Imputer >>> rsearch = RandomizedSearchCV(estimator=knn, >>> scaler = Normalizer().fit(X_train) >>> imp = Imputer(missing_values=0, strategy='mean', axis=0) param_distributions=params, >>> normalized_X = scaler.transform(X_train) >>> imp.fit_transform(X_train) cv=4, >>> normalized_X_test = scaler.transform(X_test) n_iter=8, random_state=5) Binarization Generating Polynomial Features >>> rsearch.fit(X_train, y_train) >>> print(rsearch.best_score_) >>> from sklearn.preprocessing import Binarizer >>> from sklearn.preprocessing import PolynomialFeatures >>> binarizer = Binarizer(threshold=0.0).fit(X) >>> poly = PolynomialFeatures(5) DataCamp >>> binary_X = binarizer.transform(X) >>> poly.fit_transform(X) Learn Python for Data Science Interactively.

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