Feature engineering is a crucial step in the machine learning process, and EMA (Extreme Machine Learning) takes it to the next level. By applying domain knowledge and creative techniques, EMA enables businesses to unlock business value from their data.
EMA's ability to handle high-dimensional data with ease is a significant advantage. According to a study, EMA can outperform traditional machine learning methods by up to 30% in certain cases. This is because EMA can automatically select the most relevant features from a large dataset.
By doing so, businesses can make more accurate predictions and improve their decision-making processes. For instance, a company that uses EMA to analyze customer behavior can create more effective marketing campaigns and increase sales.
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What Is Feature Engineering EMA?
Feature engineering EMA is a process that involves transforming raw data into a format that's more suitable for machine learning models. This process can significantly improve the accuracy and performance of these models.
EMA, or Exponential Moving Average, is a type of feature that can be engineered from time series data. It's calculated by taking a weighted average of past values, with more recent values given greater importance.
By applying EMA to a dataset, you can create a feature that captures the trend and momentum of the data. This can be particularly useful for forecasting and predicting future values.
For example, let's say you're working with a dataset of stock prices and you want to create a feature that captures the overall trend of the stock. You could use EMA to calculate the weighted average of past stock prices, with more recent prices given greater importance.
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Data Preparation
Data Preparation is a crucial step in feature engineering, and it's essential to handle missing data properly. The solution is to fill the missing values with statistical estimates, such as the mean, mode, or median.
You can use the `fillna` function to fill the missing values, or the `SimpleImputer` function from Scikit-learn, which requires the placeholder for the missing values and the strategy to use.
Missing data can also be treated by deleting the observations with missing feature values, dropping the feature with a large number of missing values, or substituting with averages. However, these methods may not provide good estimates for all types of observations.
To avoid recomputing work you have already done, it's essential to encapsulate dataframe transformations in functions and use a Directed Acyclic Graph (DAG) to structure data science workflows.
Here are some common techniques to treat missing values:
It's essential to understand the cause of the missing data or know if the data is missing at random before implementing any technique.
Feature Engineering Techniques
Feature engineering is the process of creating new features from existing ones to improve the performance of machine learning models. There are several techniques to achieve this.
One technique is feature extraction, which involves manipulating existing variables to create more meaningful features. For example, you can extract the hour of the day, day of the week, month, and day of the year from a timestamp.
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Another technique is creating polynomial features by crossing two or more features. This creates a relationship between the independent variables, which can result in a model with less bias.
To determine the most important features, you can use techniques such as PCA, which transforms the set of old features into a set of new features that capture most of the information. You can also use feature selection algorithms, which automatically select the best features.
Some popular feature engineering techniques include:
- Target encoding, which maps each category value to the expected value of the target for that category
- Difference and ratio techniques, which represent changes in numeric features
- Feature extraction, which manipulates existing variables to create more meaningful features
- Polynomial feature creation, which creates a relationship between independent variables
- Dimensionality reduction, which reduces the number of features to avoid the curse of dimensionality
These techniques can be used to create new features, reduce the number of features, and improve the performance of machine learning models.
EMA Basics
The EMA (Exponential Moving Average) is a popular technical indicator used in finance and trading. It's a type of moving average that gives more weight to recent prices.
The EMA formula is EMA = (Price x Multiplier) + (Previous EMA x (1 - Multiplier)), where the Multiplier is a constant between 0 and 1. This formula is used to calculate the current EMA value.
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The EMA is sensitive to recent price movements, making it a useful tool for traders who want to react quickly to changes in the market. It's often used in combination with other indicators to confirm trading signals.
The EMA can be used to identify trends, predict price movements, and set stop-loss levels. It's a versatile tool that can be applied to various financial instruments, including stocks, forex, and commodities.
Dimensionality Reduction
Dimensionality Reduction is a technique used to reduce the number of features in a dataset, making it easier to work with for certain algorithms. This is especially useful when dealing with large datasets.
Having more features can actually be a problem for some algorithms, as it can make the distance value between observations meaningless. This is known as the curse of dimensionality.
Principal Component Analysis (PCA) is a technique that can be used to reduce the number of features in a dataset. It transforms the old features into new features, keeping the ones with the highest eigenvalues.
PCA captures a lot of information with just a few features, making it a powerful tool for dimensionality reduction.
Target Encoding
Target Encoding is a technique that can help us capture the fraud risk information associated with merchants and zip codes without increasing the number of features.
This technique is particularly useful when working with a large number of categories, such as thousands of merchants, each with a different risk of fraudulent transactions. In such cases, one-hot encoding can introduce thousands of new features, which is undesirable.
Target encoding maps each category value to the expected value of the target for that category. For example, if we're working with a regression problem with a continuous target, this calculation maps the category to the mean target value for that category.
Unlike one-hot encoding, target encoding does not increase the number of features, which is a significant advantage. However, it can only be applied to supervised learning problems.
Applying target encoding may also make the model susceptible to overfitting, particularly if the number of observations in some categories is low.
Here are some scenarios where target encoding can be applied:
- MERCHANT NAME: Transactions placed against certain merchants could indicate fraudulent activity.
- TRANSACTION ZIP CODE: Transactions made in different zip codes may represent different fraud risk levels.
Engineering
Engineering is a crucial step in the feature engineering process. It involves creating new features by manipulating existing variables, which can result in more meaningful variables for the model.
You can create new features by extracting information from existing variables, such as dates or text data. For instance, you can extract the hour of the day, day of the week, month, or day of the year from a timestamp.
Feature extraction can be done using various techniques, including aggregation, transformation, and kernel methods. Regularization, feature selection, and kernel methods can help avoid feature explosion, where the number of features grows too quickly.
Dimensionality reduction techniques, such as Principal Component Analysis (PCA), can be used to reduce the number of features when dealing with the curse of dimensionality.
To create new features, you can use techniques like differences and ratios, which can represent changes in numeric features. For example, you can calculate the difference between the percent of new merchant transactions in the last 1 hour and the percent of new merchant transactions in the last 30 days.
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You can also create polynomial features by crossing two or more features, which can create a relationship between the independent variables.
Automation tools, such as featuretools, can also be used to create new features automatically. Featuretools uses a process called Deep Feature Synthesis (DFS) to generate new features.
Here are some feature engineering tools you can look at:
- Pyfeat
- Cognito
- Tsfresh
- Autofeat
These tools can help you create new features quickly and efficiently, saving you time and effort in the feature engineering process.
Data Transformations
Data transformations are a crucial step in the feature engineering process. They involve converting raw data into a format that's suitable for machine learning algorithms. Some algorithms, like Sckit-learn, can't handle missing values, while others, such as LightGBM, can handle them by default.
To ensure your data is in the right format, you need to clean it first. This involves removing missing values or replacing them with a suitable placeholder. You should also scale your data, especially if you're using distance-based algorithms like neural networks.
Here are some key things to consider when performing data transformations:
- Algorithms like Catboost can handle categorical features by default, but others may require manual handling.
- Distance-based algorithms perform poorly when data is not on the same scale, so scaling is essential.
By following these best practices, you can ensure your data is in the right format for your machine learning algorithm, and you can avoid common pitfalls like missing values and unscaled data.
Best Practices and Collaboration
Encapsulating dataframe transformations in functions is a good way to modularize a code base, but it doesn't address important questions that matter when the code grows and changes hands.
To manage feature transformation history, ensure modifications don't change feature behavior inadvertently, and know what data/feature is related to what, you need to consider how you pass input to and return from functions, and how feature transformations are related.
Here are some key considerations for collaboration in data science projects:
- Manage the feature transformation history.
- Ensure modifications don’t change feature behavior inadvertently.
- Know what data/feature is related to what.
- Version your machine learning workflow metadata and dependencies.
- Scale workflow steps by accessing necessary compute resources.
Best Practices
Feature engineering can be overwhelming, but there are some best practices to keep in mind.
First and foremost, remember that feature engineering is a necessary step to reap the benefits of a well-performing model.
You should adhere to some best practices to ensure your features are engineered correctly. This includes understanding the problem being solved by feature engineering, as mentioned earlier.
Here are some key best practices to consider:
By following these best practices, you can ensure that your feature engineering process is efficient and effective.
Data Science Collaboration
Managing a large dataset with multiple team members can be challenging. As the project evolves, it's essential to manage the feature transformation history, ensure modifications don't change feature behavior inadvertently, and know what data/feature is related to what.
To address these issues, encapsulating dataframe transformations in functions is a good start, but it doesn't solve the problem of understanding how feature transformations are related. This is where data lineage and visualization come in, making it easier to discover relationships and lineages through visualizations.
As data scientists iterate across steps in their workflows, they often need to avoid recomputing work they've already done and debug what steps in the workflow failed. This is where tools like Hamilton and Metaflow come in, asking you to structure data science code as Directed Acyclic Graphs (DAGs).
Here are some key considerations for data science collaboration:
- How do you manage the feature transformation history?
- How do you ensure modifications don’t change feature behavior inadvertently?
- How do you know what data/feature is related to what?
- How do you version your machine learning workflow metadata and dependencies?
- How does the team scale workflow steps by accessing necessary compute resources?
By following these best practices and using tools like Hamilton and Metaflow, data scientists can focus on the levels of the stack where they contribute the most and have the most leverage, reducing unnecessary computation, code base complexity, and lack of discoverability.
Implementation and Integration
Metaflow asks data scientists to structure code in Directed Acyclic Graphs (DAGs), which are referred to as steps in a flow.
In Metaflow, you can leverage branching and looping in the DAG, which is a powerful feature that allows you to create complex workflows.
Data scientists can run arbitrary Python code, such as Hamilton feature transformation DAGs, in tasks, giving them a high degree of flexibility.
Metaflow's conda integration provides robust dependency management, making it easier to manage dependencies between tasks.
Here are some key features of Metaflow's integration with DAGs:
- Branching and looping in the Metaflow DAG
- Running arbitrary Python code in tasks
- Dependency management with Metaflow’s conda integration
- Visualization of artifacts produced by steps using cards
Scaling
Scaling is a crucial step in machine learning that ensures all features have an equal opportunity to contribute to the prediction outcome. This is achieved by bringing all features on the same scale.
Tree-based algorithms like decision trees, random forest, XGBoost, and others can work with unscaled data and do not need scaling. However, other algorithms and neural networks require scaled data to function properly.
There are two common scaling techniques: normalization and standardization. Normalization restricts feature values between 0 and 1, while standardization transforms feature data distribution to the standard normal distribution.
Some common strategies for normalizing data include using the standard scaler, min max scaler, and robust scaler. The standard scaler standardizes features by removing the mean and scaling to unit-variance, while the min max scaler transforms numerical values by scaling each feature to a given range.
The process of applying the scalers involves creating an instance of the scaler, fitting it to the data, and then transforming the data. It's essential to fit the scaler to the training set and use the learned parameters to transform the testing set, as fitting to the testing set can lead to data leakage.
Here are some common scaling techniques and their characteristics:
Experimenting with different scaling techniques can help identify the one that results in a better model. However, working with a domain expert to determine the best approach can be a more reliable approach.
Hamilton and Metaflow Integration
Hamilton and Metaflow are two powerful tools that can be integrated to streamline data science workflows. Metaflow asks data scientists to structure code in Directed Acyclic Graphs (DAGs), referred to as steps in a flow.
In this integration, Metaflow's DAG structure is used to orchestrate the execution of Hamilton DAGs, which model specific aspects of the data science workflow, such as feature transformation. Hamilton's @extract_columns decorator is used to extract columns from dataframes and make them individually available for consumption.
The numeric feature transformation functions are defined in normalized_features.py, which contains functions to extract specific columns from dataframes. For example, one function extracts the mean age of people represented in data records.
To run Hamilton DAGs in Metaflow, a Hamilton Driver is instantiated and executed, requesting the features and outputs that are needed. This is done in two steps of a Metaflow flow: featurize_and_split and feature_importance_merge.
Here's an overview of the Hamilton features used in the Metaflow flow:
- branching and looping in the Metaflow DAG
- running arbitrary Python code – such as Hamilton feature transformation DAGs – in tasks
- dependency management with Metaflow’s conda integration
- cards to visualize artifacts produced by steps
In the featurize_and_split step, the Hamilton Driver code is executed to select all features. In the feature_importance_merge step, only the top k features are selected based on a feature selection policy applied to the outputs of earlier steps in the DAG.
The Solution
Feature engineering is a key part of the solution, as it allows you to get the best possible results from your data and algorithm.
Obtaining optimal features will often lead to better performance, even when using less complex models. This is because feature engineering ensures that you're working with the most valuable data, which can make a big difference in the outcome.
Feature engineering isn't one-size-fits-all, so you'll need to tailor your approach to the specific problem at hand. This might require some experimentation and trial-and-error, but it's worth it in the end.
By focusing on feature engineering, you can unlock the full potential of your data and algorithm, leading to better performance and more accurate results.
Frequently Asked Questions
What are the 4 main processes of feature engineering?
The four main processes of feature engineering are Feature Creation, Transformations, Feature Extraction, and Feature Selection. These steps help identify and prepare the most useful variables for a predictive model.
What is feature engineering in demand forecasting?
Feature engineering in demand forecasting is the process of selecting and transforming input data to create strong relationships between features and actual demand values. This involves choosing the most relevant features based on the specific time series being analyzed.
Sources
- https://towardsdatascience.com/feature-engineering-for-machine-learning-eb2e0cff7a30
- https://cnvrg.io/feature-engineering/
- https://datascience.stackexchange.com/questions/22089/difference-between-feature-engineering-and-feature-learning
- https://outerbounds.com/blog/developing-scalable-feature-engineering-dags
- https://www.linkedin.com/pulse/10-feature-engineering-techniques-machine-learning-muctary-abdallah
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