辅导案例-CSCI3151-Assignment 4

  • July 18, 2020

Assignment 4 – Foundations of Machine Learning CSCI3151 – Dalhousie University Q1 (30%) Clustering In this question we are going to explore two different clustering methods on the ​wine dataset and evaluate it using two measures: one is an intrinsic measure (no labels), while the other one makes use of the available labels. a) Cluster the dataset using the k-Means clustering algorithm without using the class information as part of the features. Experiment with different numbers of clusters ranging from 2 to 5. What is the variability of the resulting clusters as a function of different initializations? Use the Silhouette coefficient and Adjusted Rand Index as metrics for evaluation. b) Cluster the dataset using DBSCAN without using the class information as part of the features. Experiment with different values for the parameters Eps and minPts. It’s up to you how you deal with any outliers, but make sure your criterion is properly justified. What is the variability of the resulting clusters as a function of different initializations? Use the Silhouette coefficient and Adjusted Rand Index as metrics for evaluation. c) Summarize your findings and comparison after experimenting with these two clustering methods. Q2 (40%) Convolutional neural networks In this question you will construct a convolutional neural network to classify a large set of low resolution images. Similarly to what you have done with A2, we would like you to describe the behavior of the network as you modify certain parameters. Use the CIFAR-100 dataset (available from Keras) from keras.datasets import cifar100 (x_train_original, y_train_original), (x_test_original, y_test_original) = cifar100.load_data(label_mode=’fine’) a) Using two convolutional layers, explore the impact on different choices for the number of nodes and filter sizes for the two layers. Summarize your observations. b) For the hyperparameters for the layers that you determined in part (a), experiment with a higher number of epochs. Summarize your observations. c) Experiment with two more activation functions in the convolutional layers using the optimal number of epochs from part (b). Are you able to improve the validation accuracy? d) For the result in (c), calculate test accuracy for each class. Do you observe lower accuracy for any specific class or classes? Do you observe higher accuracy for any specific class or classes? Q3 (30%) Recurrent Neural Networks In this question you will experiment with a simple recurrent neural network, where you will try to model a sinusoidal function with noise, whose amplitude becomes larger and larger as the independent variable ​t increases ( ). This function can be expressed in Python as 0 ≤ t ≤ N x=(np.sin(0.02*t)+2*np.random.rand(N))*(t/N) . For N=5000 we have: The idea is that you will train a recurrent neural network with points up to a certain value, ​Tp​. This is all the training points will be . The length of the sequence provided to the network pt ≤ T is a parameter that you can tune. You will use the notebook provided for this question named “A4Q3.ipynb” a) Complete the notebook provided to fulfill this task. You need to add at least one simpleRNN layer​ and a proper output layer. b) Starting with ​length = 4, ​discuss how different choices of the length of the sequence fed to the network can have an impact on performance. c) Discuss how different network architectures can have an impact on performance. Note 1: for simplicity, ​don’t change ​the values of the variables ​N​ and ​Tp​. Note 2: make sure you understand the code before addressing these questions. Submitting the assignment Note that you will have three separate Assignments 4 on Brightspace, i.e. one for each question (A4-Q1, A4-Q2, and A4-Q3) 1. Your assignment as a single .ipynb file including your answers should be submitted for each question before the deadline on Brightspace. Use ​markdown​ syntax to format your answers. 2. Do not clear your notebook. Keep all the results in your notebook. (​NEW​) 3. You can submit multiple editions of your assignment. Only the last one will be marked. It is recommended to upload a complete submission, even if you are still improving it, so that you have something into the system if your computer fails for whatever reason. 4. IMPORTANT: PLEASE NAME YOUR PYTHON NOTEBOOK FILE AS: –Assignment-N-Q.ipynb, for example Soto-Axel-Assignment-2-1.ipynb (for the first question of the second assignment) A penalty applies if the format is not correct. 5. The markers will enter your marks and their overall feedback on Brightspace. In case that there is any important feedback, it will be given to you, but otherwise you would need to refer to the model solutions. Marking the assignment Criteria and weights. Each criterion is marked by a letter grade. Overall mark is the weighted average of the grade of each criterion. For the experimental questions: 0.2 Clarity: All steps are clearly described. The origin of all code used is clearly. Markdown is used effectively to format the answer to make it easier to read and grasp the main points. Links have been added to all online resources used (markdown syntax is: [AnchorText](URL) ). 0.2 Justification: Parameter choices or processes are well justified. 0.2 Results: The results are complete. The results are presented in a manner that is easy to understand. The answer is selective in the amount and diversity of the experimental results presented. Only key results that support the insights are presented. There is no need to present every single experiment you carried out. Only the interesting results are presented, where the behaviour of the ML model varies. 0.4 Insights: The insights obtained from the experimental results are clearly explained. The insights are connected with the concepts discussed in the lectures. The insights can also include statistical considerations (separate training-test data, cross-validation, variance).Preliminary investigation of the statistical properties of the attributes (e.g. histogram, mean, standard deviation) is included.

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