# Coursera machine learning week 9 assignment answers – Andrew Ng

In this article, you will find Coursera machine learning week 9 assignment answers – Andrew Ng.  Use “Ctrl+F” To Find Any Questions or Answers. For Mobile Users, You Just Need To Click On Three dots In Your Browser & You Will Get A “Find” Option There. Use These Options to Get Any Random Questions Answer.

Try to solve all the assignments by yourself first, but if you get stuck somewhere then feel free to browse the code. Don’t just copy-paste the code for the sake of completion.  Even if you copy the code, make sure you understand the code first.

In this exercise, you will implement the anomaly detection algorithm and apply it to detect failing servers on a network. In the second part, you will use collaborative filtering to build a recommender system for movies. Before starting on the programming exercise, we strongly recommend watching the video lectures and completing the review questions for the associated topics.

### Coursera machine learning week 9 assignment answers

```function [mu sigma2] = estimateGaussian(X)
%ESTIMATEGAUSSIAN This function estimates the parameters of a
%Gaussian distribution using the data in X
%   [mu sigma2] = estimateGaussian(X),
%   The input X is the dataset with each n-dimensional data point in one row
%   The output is an n-dimensional vector mu, the mean of the data set
%   and the variances sigma^2, an n x 1 vector
%
% Useful variables
[m, n] = size(X);
% You should return these values correctly
mu = zeros(n, 1);
sigma2 = zeros(n, 1);
% ====================== YOUR CODE HERE ======================
% Instructions: Compute the mean of the data and the variances
%               In particular, mu(i) should contain the mean of
%               the data for the i-th feature and sigma2(i)
%               should contain variance of the i-th feature.
%
mu = ((1/m)*sum(X))';
sigma2 = ((1/m)*sum((X-mu').^2))';
% =============================================================
end```
```function [bestEpsilon bestF1] = selectThreshold(yval, pval)
%SELECTTHRESHOLD Find the best threshold (epsilon) to use for selecting
%outliers
%   [bestEpsilon bestF1] = SELECTTHRESHOLD(yval, pval) finds the best
%   threshold to use for selecting outliers based on the results from a
%   validation set (pval) and the ground truth (yval).
%
bestEpsilon = 0;
bestF1 = 0;
F1 = 0;
stepsize = (max(pval) - min(pval)) / 1000;
for epsilon = min(pval):stepsize:max(pval)
% ====================== YOUR CODE HERE ======================
% Instructions: Compute the F1 score of choosing epsilon as the
%               threshold and place the value in F1. The code at the
%               end of the loop will compare the F1 score for this
%               choice of epsilon and set it to be the best epsilon if
%               it is better than the current choice of epsilon.
%
% Note: You can use predictions = (pval < epsilon) to get a binary vector
%       of 0's and 1's of the outlier predictions
cvPredictions = (pval < epsilon);     % m x 1
tp = sum((cvPredictions == 1) & (yval == 1)); % m x 1
fp = sum((cvPredictions == 1) & (yval == 0)); % m x 1
fn = sum((cvPredictions == 0) & (yval == 1)); % m x 1
prec = tp/(tp+fp);
rec = tp/(tp+fn);
F1 = 2*prec*rec / (prec + rec);
% =============================================================
if F1 > bestF1
bestF1 = F1;
bestEpsilon = epsilon;
end
end
end
```
```function [J, grad] = cofiCostFunc(params, Y, R, num_users, num_movies, ...
num_features, lambda)
%COFICOSTFUNC Collaborative filtering cost function
%   [J, grad] = COFICOSTFUNC(params, Y, R, num_users, num_movies, ...
%   num_features, lambda) returns the cost and gradient for the
%   collaborative filtering problem.
%
% Unfold the U and W matrices from params
X = reshape(params(1:num_movies*num_features), num_movies, num_features);
Theta = reshape(params(num_movies*num_features+1:end), ...
num_users, num_features);
% You need to return the following values correctly
J = 0;
X_grad = zeros(size(X));            % Nm x n
Theta_grad = zeros(size(Theta));    % Nu x n
% ====================== YOUR CODE HERE ======================
% Instructions: Compute the cost function and gradient for collaborative
%               filtering. Concretely, you should first implement the cost
%               function (without regularization) and make sure it is
%               matches our costs. After that, you should implement the
%               gradient and use the checkCostFunction routine to check
%               that the gradient is correct. Finally, you should implement
%               regularization.
%
% Notes: X - num_movies  x num_features matrix of movie features
%        Theta - num_users  x num_features matrix of user features
%        Y - num_movies x num_users matrix of user ratings of movies
%        R - num_movies x num_users matrix, where R(i, j) = 1 if the
%            i-th movie was rated by the j-th user
%
% You should set the following variables correctly:
%
%        X_grad - num_movies x num_features matrix, containing the
%                 partial derivatives w.r.t. to each element of X
%        Theta_grad - num_users x num_features matrix, containing the
%                     partial derivatives w.r.t. to each element of Theta
%
%% %%%%% WORKING: Without Regularization %%%%%%%%%%
Error = (X*Theta') - Y;
J = (1/2)*sum(sum(Error.^2.*R));
X_grad = (Error.*R)*Theta;   % Nm x n
Theta_grad = (Error.*R)'*X;  % Nu x n
%% %%%%% WORKING: With Regularization
Reg_term_theta = (lambda/2)*sum(sum(Theta.^2));
Reg_term_x = (lambda/2)*sum(sum(X.^2));
J = J + Reg_term_theta + Reg_term_x;
% =============================================================
end```

Disclaimer:  Hopefully, this article will be useful for you to find all the Coursera machine learning week 9 assignment answers and grab some premium knowledge with less effort.

Finally, we are now, in the end, I just want to conclude some important message for you, Feel free to ask doubts in the comment section. I will try my best to answer it. If you find this helpful by any means like, comment, and share the post. Please share our posts on social media platforms and also suggest to your friends to Join Our Groups. Don’t forget to subscribe. This is the simplest way to encourage me to keep doing such work.

### FAQs

Is Andrew Ng’s Machine Learning course good?
It is the Best Course for Supervised Machine Learning! Andrew Ng Sir has been like always has such important & difficult concepts of Supervised ML with such ease and great examples, Just amazing!

How do I get answers to coursera assignment?
Use “Ctrl+F” To Find Any Questions Answered. & For Mobile Users, You Just Need To Click On Three dots In Your Browser & You Will Get A “Find” Option There. Use These Options to Get Any Random Questions Answer.

How long does it take to finish coursera Machine Learning?
this specialization requires approximately 3 months with 75 hours of materials to complete, and I finished it in 3 weeks and spent an additional 1 week reviewing the whole course.

How do you submit assignments on Coursera Machine Learning?
Submit a programming assignment Open the assignment page for the assignment you want to submit. Read the assignment instructions and download any starter files. Finish the coding tasks in your local coding environment. Check the starter files and instructions when you need to. Reference

Sharing Is Caring