Mercurial > hg > tvii
diff tvii/logistic_regression.py @ 32:0f29b02f4806
[logistic regression] add model
author | Jeff Hammel <k0scist@gmail.com> |
---|---|
date | Mon, 04 Sep 2017 13:20:25 -0700 |
parents | fa7a51df0d90 |
children | e2dd9503098f |
line wrap: on
line diff
--- a/tvii/logistic_regression.py Mon Sep 04 12:37:45 2017 -0700 +++ b/tvii/logistic_regression.py Mon Sep 04 13:20:25 2017 -0700 @@ -136,3 +136,79 @@ grads = {"dw": dw, "db": db} return params, grads, costs + + +def predict(w, b, X): + ''' + Predict whether the label is 0 or 1 using learned logistic regression parameters (w, b) + + Arguments: + w -- weights, a numpy array of size (num_px * num_px * 3, 1) + b -- bias, a scalar + X -- data of size (num_px * num_px * 3, number of examples) + + Returns: + Y_prediction -- a numpy array (vector) containing all predictions (0/1) for the examples in X + ''' + + m = X.shape[1] + Y_prediction = np.zeros((1,m)) + w = w.reshape(X.shape[0], 1) + + # Compute vector "A" predicting the probabilities + A = sigmoid(np.dot(w.T, X) + b) + + for i in range(A.shape[1]): + # Convert probabilities A[0,i] to actual predictions p[0,i] + Y_prediction[0][i] = 0 if A[0][i] <= 0.5 else 1 + + assert(Y_prediction.shape == (1, m)) + + return Y_prediction + + +def model(X_train, Y_train, X_test, Y_test, num_iterations = 2000, learning_rate = 0.5, print_cost = False): + """ + Builds the logistic regression model by calling the function you've implemented previously + + Arguments: + X_train -- training set represented by a numpy array of shape (num_px * num_px * 3, m_train) + Y_train -- training labels represented by a numpy array (vector) of shape (1, m_train) + X_test -- test set represented by a numpy array of shape (num_px * num_px * 3, m_test) + Y_test -- test labels represented by a numpy array (vector) of shape (1, m_test) + num_iterations -- hyperparameter representing the number of iterations to optimize the parameters + learning_rate -- hyperparameter representing the learning rate used in the update rule of optimize() + print_cost -- Set to true to print the cost every 100 iterations + + Returns: + d -- dictionary containing information about the model. + """ + + # initialize parameters with zeros + raise NotImplementedError('TODO') # -> record TODO items + w, b = initialize_with_zeros(X_train.shape[0]) + + # Gradient descent + parameters, grads, costs = optimize(w, b, X_train, Y_train, num_iterations, learning_rate, print_cost=print_cost) + + # Retrieve parameters w and b from dictionary "parameters" + w = parameters["w"] + b = parameters["b"] + + # Predict test/train set examples + Y_prediction_test = predict(w, b, X_test) + Y_prediction_train = predict(w, b, X_train) + + + # Print train/test Errors + print("train accuracy: {} %".format(100 - np.mean(np.abs(Y_prediction_train - Y_train)) * 100)) + print("test accuracy: {} %".format(100 - np.mean(np.abs(Y_prediction_test - Y_test)) * 100)) + + d = {"costs": costs, + "Y_prediction_test": Y_prediction_test, + "Y_prediction_train" : Y_prediction_train, + "w" : w, + "b" : b, + "learning_rate" : learning_rate, + "num_iterations": num_iterations} + return d