Over Sampling methods IMBLEARN Package Realised by : Rida benbouziane.

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1 Over Sampling methods IMBLEARN Package Realised by : Rida benbouziane

2 Plan Introduction : Data Sampling and Data Imbalance Techniques to solve the class imbalance problem Different between under sampling and oversampling Methods of oversampling Installation & implementation Conclusion

3 Introduction : Sampling and Data Imbalance Data Imbalance ? types of sampling ? Sampling ?

4 Techniques to solve the imbalance problem Resampling (Oversampling and Undersampling) Ensembling Methods (Ensemble of Sampler)

5 Techniques to solve the imbalance problem List of the methods Under-sampling Random majority under-sampling with replacement Extraction of majority-minority Tomek links Under-sampling with Cluster Centroids NearMiss-(1 & 2 & 3) Condensed Nearest Neighbou One-Sided Selection Neighboorhood Cleaning Rule Edited Nearest Neighbours Instance Hardness Threshold Repeated Edited Nearest Neighbours AllKNN Over-sampling Random minority over-sampling with replacement SMOTE - Synthetic Minority Over-sampling Technique bSMOTE(1 & 2) - Borderline SMOTE of types 1 and 2 SVM SMOTE - Support Vectors SMOTE ADASYN - Adaptive synthetic sampling approach for imbalanced learning Over-sampling followed by under-sampling SMOTE + Tomek links SMOTE + ENN Ensemble classifier using samplers internally EasyEnsemble BalanceCascade Balanced Random Forest Balanced Bagging

6 Different between under sampling and oversampling

7 Methods of oversampling Random oversampling for the minority class Synthetic Minority Oversampling Technique (SMOTE) ADASYN: Adaptive Synthetic Sampling

8 Random oversampling for the minority class Figure 1

9 Synthetic Minority Oversampling Technique (SMOTE) Figure 1 Figure 3Figure 2

10 ADASYN: Adaptive Synthetic Sampling ADASYN (Adaptive Synthetic) is an algorithm that generates synthetic data, and its greatest advantages are not copying the same minority data, and generating more data for “harder to learn” examples.The biggest advantages of ADASYN are it’s adaptive nature of creating more data for “harder-to-learn” examples and allowing you to sample more negative data for your model. Using ADASYN, you can ultimately synthetically balance your data set!

11 ADASYN: Adaptive Synthetic Sampling First, ADASYN calculates the ratio of minority to majority observations Next, ADASYN computes the total number of synthetic minority data to generate: G is the total number of synthetic minority data to generate and ß denotes the ratio of minority to majority observations. Thus, ß = 1 would mean that there are equally as many observations in both classes after using ADASYN. Third, ADASYN finds the k-nearest neighbors for each of the minority observations and computes an r value: The r value measures the dominance of the majority class in the neighborhood. The higher r, the more dominant the majority class and the more difficult the neighborhood is to learn for your classifier. Let us calculate r for some fictional minority observation: Figure 1 Figure 2 Figure 3

12 ADASYN: Adaptive Synthetic Sampling Next, ADASYN computes the number of synthetic observations to generate in each neighborhood: Finally, ADASYN generates synthetic observations: Figure 4 Figure 1

13 Installation & implementation conda install -c conda-forge imbalanced-learn

14 Conclusion Dealing with imbalanced data can be extremely challenging. imbalanced data should become a lot less intimidating. Besides over-sampling, there are several other ways to attack minority, such as under-sampling or combinations of the two.

15 https://www.healthknowledge.org.uk/public-health-textbook/research- methods/1a-epidemiology/methods-of-sampling-population https://towardsdatascience.com/sampling-techniques-for-extremely- imbalanced-data-part-ii-over-sampling-d61b43bc4879 https://towardsdatascience.com/having-an-imbalanced-dataset-here-is-how- you-can-solve-it-1640568947eb https://towardsdatascience.com/a-deep-dive-into-imbalanced-data-over- sampling-f1167ed74b5 Refferences

16 Over Sampling methods IMBLEARN Package Realised by : Rida benbouziane Soufiane Boukroum