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Data Preprocessing || Data Mining
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- 2. HELLO! I am IffatFirozy I am here because I love to teach. 2
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- 4. “Data preprocessing isa data mining technique which is used to transform the raw data in a useful and efficient format.” 4
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- 6. We preprocess thedata for better - 6
- 7. MAJOR TASK INDATA PREPROCESSING 7
- 8. 8 DATA PREPROCESSING DATA CLEANING MISSINGVALUES NOISY DATA DATA INTEGRATION DETECTION AND RESOLUTION REDUNDANT ATTRIBUTES SCEMA INTREGATION DATA TRANSFORMATION NORMALIZATION ATTRIBUTE SELECTION DISCRITIZATION DATA REDUCTION NUMEROCITY REDUCTION DATA COMPRESSION DIMONTIONALITY REDUCTION
- 9. Data Cleaning Missing values Thissituation arises when some data is missing in the data. It can be handled in various ways. Some of them are: ❑ Ignore the tuples: This approach is suitable only when the dataset we have is quite large and multiple values are missing within a tuple. ❑ Fill the Missing values: There are various ways to do this task. You can choose to fill the missing values manually, by attribute mean or the most probable value. 9 The data can have many irrelevant and missing parts. To handle this part, data cleaning is done. It involves handling of missing data, noisy data etc.
- 10. Continue… Noisy Data Noisy datais a meaningless data that can’t be interpreted by machines. It can be generated due to faulty data collection, data entry errors etc. It can be handled in following ways : Binning Method: This method works on sorted data in order to smooth it. The whole data is divided into segments of equal size and then various methods are performed to complete the task. Each segmented is handled separately. One can replace all data in a segment by its mean or boundary values can be used to complete the task. ❑ Regression: Here data can be made smooth by fitting it to a regression function. The regression used may be linear (having one independent variable) or multiple (having multiple independent variables). ❑ Clustering: This approach groups the similar data in a cluster. The outliers may be undetected or it will fall outside the clusters. 10
- 11. Data Integration Data analysismay require a combination of data from multiple sources into a coherent data store. Schema integration: CID = C_number = Cust-id = cust# Data value conflicts (different representations or scales, etc.) Synchronization (especially important in Web usage mining) Redundant attributes (redundant if it can be derived from other attributes) 11
- 12. DATA TRANSFORMATION 12 This stepis taken in order to transform the data in appropriate forms suitable for mining process. This involves following ways: Normalization: It is done in order to scale the data values in a specified range (-1.0 to 1.0 or 0.0 to 1.0) Attribute Selection: In this strategy, new attributes are constructed from the given set of attributes to help the mining process. Discretization: This is done to replace the raw values of numeric attribute by interval levels or conceptual levels. Concept Hierarchy Generation: Here attributes are converted from level to higher level in hierarchy. For Example-The attribute “city” can be converted to “country”.
- 13. DATA REDUCTION 13 Since datamining is a technique that is used to handle huge amount of data. While working with huge volume of data, analysis became harder in such cases. In order to get rid of this, we uses data reduction technique. It aims to increase the storage efficiency and reduce data storage and analysis costs. The various steps to data reduction are: Numerosity Reduction: This enable to store the model of data instead of whole data, for example: Regression Models. Dimensionality Reduction: This reduce the size of data by encoding mechanisms. It can be lossy or lossless. If after reconstruction from compressed data, original data can be retrieved, such reduction are called lossless reduction else it is called lossy reduction. The two effective methods of dimensionality reduction are: Wavelet transforms and PCA (Principal Component Analysis).
- 14. 14 THANKS! Any questions? You canfind me at: ❑ ifirozy@gmail.com