The holy grail of data cleaning is a system that does it for you. BoostClean is our first step towards this vision.
Many data science projects and companies follow the process of collecting (dirty) data from a variety of domains, performing extensive data cleaning, and then developing a model. Ideally the data cleaning effort will actually improve the quality of the model (but as ActiveClean showed, this may not be the case!) In addition, a huge amount of time is spent addressing simple but tedious errors such as outlier removal, duplicate elimination, imputation, etc. These are structurally similar, but distinct for every domain and dataset. Thus the data scientist goes through a list of data cleaning functions (e.g., Python cleaning functions) and manually checks if they apply; if so, then how to parameterize the functions.
BoostClean attempts to automate this process by treating it as a boosting problem. Each data cleaning operation effectively adds a new cleaning feature to the input of the downstream ML model, and a combination of Boosting and feature selection can be used to identify a good sequence of cleaning operations that will best improve the ML model!
Databases can be corrupted with various errors such as missing, incorrect, or inconsistent values. Increasingly, modern data analysis pipelines involve Machine Learning, and the effects of dirty data can be difficult to debug. Dirty data is often sparse, and naive sampling solutions are not suited for high-dimensional models. The following figures show how data cleaning can degrade the machine learning model.
Shows how systematic corruption of data (from circles to crosses) can lead to a shifted, incorrect model.
Illustrates the true model if the full dataset were cleaned.
Shows how combining two cleaned records (blue) with the dirty records leads to a worse model than no cleaning.
Shows how only using the two cleaned records can also result in a worse model due to sampling error.
ActiveClean is an iterative cleaning framework that can correctly retrain the machine learning model when data is cleaned, and provides a set of optimizations to select the best data to be cleaned. In this way, you only need to clean a small subset of the data in order to produce a model similar to if the full dataset were cleaned.
The ActiveClean codebase is written in Python and includes the core ActiveClean algorithm, a data cleaning benchmark, and (in the future), an dirty data detector:
The Data Cleaning Benchmark automatically injects data errors into your datasets to test the robustness of your machine learning models to data errors. It can be installed using pip:
pip install cleaningbenchmark
To reproduce our results and run the code, simply download the files in the following link and run the python file using:
The script is quite simple, so you can read it to see everything in action.
ActiveClean is a collaboration between the WuLab at Columbia University, the AMPLab at University of California, Berkeley, and Jiannan Wang at Simon Fraser University.