Andrew Ng's Machine Learning course learning (WEEK5) Neural Network Learning

Source: Internet
Author: User

This semester has been to follow up on the Coursera Machina learning public class, the teacher Andrew Ng is one of the founders of Coursera, machine learning aspects of Daniel. This course is a choice for those who want to understand and master machine learning. This course covers some of the basic concepts and methods of machine learning, and the programming of this course plays a huge role in mastering these concepts and methods.

Course Address

The main notes are a summary of the course content, as well as MATLAB programming work ....

Neural Networks

WEEK4 Programming Job Core Code


1%First, the original label representation of y into the vector mode output 2 Y_vect = zeros (m,num_labels); %5000x10 3 For i = 1: M, 4 y_vect (I,y (i)) = 1; 5End 6 7 a1 = [Ones (M, 1) X]; 8 z2 = A1 * Theta1 ';    9 A2 = sigmoid (z2); % x 2510 a2 = [Ones (m,1) A2];   % x 2611 z3 = A2 * Theta2 ';    % x 1012 a3 = sigmoid (Z3); % 1013 x for i = 1: M15 j = j + sum ( -1*y_vect (i,:). *log (A3 (I,:))-(1-y_vect (i,:)). *log (1-A3 (I,:))); end17 j = j/m;18 j = j + lambda* (sum (SUM (Theta1 (:, 2:end). ^2)) +sum (SUM (THETA2 (:, 2:end). ^2))/2/m;%
              backward Propagation Delta1 = zeros (Size (Theta1)); %
              25x40122 Delta2 = zeros (Size (THETA2));%10x2623 for I=1: M24 delta3 = A3 (i,:) '-Y_vect (i,:) ';%10x125 tempTheta2 = Theta2 ' * DELTA3; % 26x10x10x1 = 26x1-Delta2 = TempTheta2 (2:end). * Sigmoidgradient (Z2 (i,:) ');%25x1 Delta2 = Delta2 + delta3 * A2 (I,: ); % 10x1x1x2628 Delta1 = Delta1 + delta2 * A1 (i,:);%25x1x1x40129 end; Theta2_grad = delta2/m; Ta1_grad = delta1/m;regularization gradient Theta2_grad (:, 2:end) = Theta2_grad (:, 2:end) + lambda * Theta2 (:, 2:end)/ m; PNs Theta1_grad (:, 2:end) = Theta1_grad (:, 2:end) + lambda * Theta1 (:, 2:end)/ m; 


1 g = sigmoid (z). * (1-sigmoid (z));

Andrew Ng's Machine Learning course learning (WEEK5) Neural Network Learning

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.