Techniques for Feature Engineering

Feature engineering is a crucial step in any data science project as it involves selecting and creating the most relevant features that will be used to train machine learning models. By properly engineering the features, we can improve the performance and accuracy of our models. In this article, we will discuss some common techniques and strategies for feature engineering in the context of data science with Python.

1. Handling Missing Values

Missing values in a dataset can significantly impact the performance of our models. There are various techniques to handle missing values, such as:

  • Imputation: Replacing missing values with a reasonable estimate. This can be done by taking the mean, median, or mode of the available data.
  • Creating a Missing Indicator: Introducing a boolean feature that represents whether a value was missing or not. This can capture the information from missing values and may improve the model's performance.
  • Dropping Rows or Columns: In some cases, if the missing values are too many or the feature itself is not important, we can choose to drop the rows or columns with missing values.

2. Encoding Categorical Variables

Categorical variables are non-numerical variables that represent different categories or groups. Machine learning models typically require numerical inputs, so we need to convert categorical variables into a numerical form. Some common techniques for categorical variable encoding include:

  • One-Hot Encoding: Creating binary features for each category in a categorical variable. Each feature represents whether the corresponding category is present or not.
  • Label Encoding: Assigning a numerical label to each category. This can be useful for ordinal variables where the order of categories matters.
  • Target Encoding: Replacing each category with the average target value for that category. This can be helpful when the target variable is correlated with the categorical variable.

3. Feature Scaling

Feature scaling is important for many machine learning algorithms as it helps bring all features to a common scale. Some common techniques for feature scaling include:

  • Standardization: Transforming the feature values to have zero mean and unit variance. This is done by subtracting the mean and dividing by the standard deviation of the feature.
  • Normalization: Scaling the feature values to a range between 0 and 1. This is achieved by subtracting the minimum and dividing by the range of the feature.

4. Feature Interaction and Polynomial Features

Sometimes, the relationship between features and the target variable is not linear, and by creating interactions or transforming the features to higher degrees, we can capture more complex patterns. Some techniques for feature interaction and polynomial features include:

  • Interaction Features: Creating new features by combining two or more existing features. This can be done by taking the product, sum, or difference of the original features.
  • Polynomial Features: Creating new features by raising the existing features to higher degrees. This can capture nonlinear relationships between the features and the target variable.


Feature engineering plays a crucial role in machine learning projects as it helps improve the performance and accuracy of models. In this article, we discussed some common techniques for feature engineering, including handling missing values, encoding categorical variables, feature scaling, and creating interaction and polynomial features. By applying these techniques, we can enhance the quality of our features and develop more robust machine learning models.

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