Big Data Analysis and Mining Lecture 2: Data Preprocessing Weixiong Rao饶卫雄 Tongji University同济大学软件学院 2015 Fall wxrao@tongji.edu.cn Some of the slides are from Dr Jure Leskovec's and Prof. Zachary G Ives 2021/28 同济大学软件学院 ool of Software Engineering. Tongpi Unversity
2021/2/8 1 Big Data Analysis and Mining Lecture 2: Data Preprocessing Weixiong Rao 饶卫雄 Tongji University 同济大学软件学院 2015 Fall wxrao@tongji.edu.cn *Some of the slides are from Dr Jure Leskovec’s and Prof. Zachary G. Ives
Data Preprocessing a Data Preprocessing: An Overview ◆ Data Quality Major Tasks in Data Preprocessing a Data Cleaning u Data Integration ■ Data reduction Data Transformation and data discretization ■ Summary 同济大学软件学院 ool of Software Engineering. Tongpi Unversity
2 2 Data Preprocessing ◼ Data Preprocessing: An Overview ◆ Data Quality ◆ Major Tasks in Data Preprocessing ◼ Data Cleaning ◼ Data Integration ◼ Data Reduction ◼ Data Transformation and Data Discretization ◼ Summary
Data Quality: Why Preprocess the Data? a Measures for data quality: A multidimensional view Accuracy: correct or wrong, accurate or not ◆ Completeness: not recorded, unavailable,… Consistency: some modified but some not, dangling Timeliness: timely update? e Believability how trustable the data are correct? Interpretability how easily the data can be understood? 同济大学软件学院 3 ool of Software Engineering. Tongpi Unversity
3 Data Quality: Why Preprocess the Data? ◼ Measures for data quality: A multidimensional view ◆ Accuracy: correct or wrong, accurate or not ◆ Completeness: not recorded, unavailable, … ◆ Consistency: some modified but some not, dangling ◆ Timeliness: timely update? ◆ Believability: how trustable the data are correct? ◆ Interpretability: how easily the data can be understood?
Major Tasks in Data Preprocessing Data cleaning Fill in missing values, smooth noisy data, identify or remove outliers and resolve inconsistencies Data integration Integration of multiple databases, data cubes, or files Data reduction Dimensionality reduction ◆ Numerosity reduction ◆ Data compression Data transformation and data discretization ◆ Normalization Concept hierarchy generation 同济大学软件学院 ool of Software Engineering. Tongpi Unversity
4 Major Tasks in Data Preprocessing ◼ Data cleaning ◆ Fill in missing values, smooth noisy data, identify or remove outliers, and resolve inconsistencies ◼ Data integration ◆ Integration of multiple databases, data cubes, or files ◼ Data reduction ◆ Dimensionality reduction ◆ Numerosity reduction ◆ Data compression ◼ Data transformation and data discretization ◆ Normalization ◆ Concept hierarchy generation
Data Preprocessing a Data Preprocessing: An Overview ◆ Data Quality Major Tasks in Data Preprocessing a Data Cleaning u Data Integration ■ Data reduction Data Transformation and data discretization ■ Summary 同济大学软件学院 ool of Software Engineering. Tongpi Unversity
5 5 Data Preprocessing ◼ Data Preprocessing: An Overview ◆ Data Quality ◆ Major Tasks in Data Preprocessing ◼ Data Cleaning ◼ Data Integration ◼ Data Reduction ◼ Data Transformation and Data Discretization ◼ Summary