How Does Lasso Regression works?

Lasso regression is fundamentally an extension of linear regression. The goal of traditional linear regression is to minimize the sum of squared differences between the observed and predicted values in order to determine the line that best fits the data points. But the complexity of real-world data is not taken into account by linear regression, particularly when there are many factors.

1. Ordinary Least Squares (OLS) Regression: Lasso regression is very useful in this situation because adding a penalty term In lasso regression, minimize the sum of squared differences. The predictors’ coefficients’ absolute values serve as the basis for this penalty. The formula for OLS is:

min [Tex]RSS = Σ(yᵢ – ŷᵢ)²[/Tex]

Where,

  • [Tex]y_i[/Tex] is the observed value.
  • and [Tex]ŷᵢ[/Tex] is the predicted value for each data point i.

2. Penalty Term for Lasso Regression: The OLS equation is supplemented with a penalty term. This penalty term is the sum of the absolute values of the coefficients (also known as L1 regularization). The goal is now to minimize the penalty term plus the sum of squared differences:

[Tex]RSS + \lambda \times \sum |\beta_i|[/Tex]

Where,

  • [Tex]\beta_i[/Tex] represents the coefficients of the predictors
  • and [Tex]\lambda[/Tex] is the tuning parameter that controls the strength of the penalty. As lambda increases, more coefficients are pushed towards zero

3. Shrinking Coefficients: The penalty term in lasso regression have a unique characteristic with is its ability to reduce the coefficients of less significant variables to zero. As a result, features with zero coefficients are eliminated from the model, essentially performing variable selection. When working with high-dimensional data where there are many predictors relative to the number of observations this is especially helpful.

Lasso regression makes the model simpler and less prone to overfitting by reducing or deleting the coefficients of unimportant predictors. This improves the model’s readability and ability to be applied to fresh sets of data.

4. Selecting the optimal [Tex]\lambda[/Tex]: In lasso regression, selecting the tuning parameter lambda is essential. Frequently, cross-validation methods are employed to determine the ideal value of lambda that strikes a balance between predicted accuracy and model complexity.

The primary objective of Lasso regression is to minimize the residual sum of squares (RSS) along with a penalty term multiplied by the sum of the absolute values of the coefficients.


In the plot, the equation for the Lasso Regression of cost function, combines the residual sum of squares (RSS) and an L1 penalty on the coefficients [Tex]β_j[/Tex].

  • RSS measures: The squared difference between the expected and actual values is measured.
  • L1 penalty: Penalizes the coefficients’ absolute values, bringing some of them to zero and simplifying the model. The L1 penalty’s strength is managed via the lambda term. Stronger penalties result from greater lambdas, which may both increase the RSS and make the model sparser (having more coefficients equal to zero).

The graph itself shows the relationship between the value of lambda (x-axis) and the cost function (y-axis).

  • y-axis: represents the value of the cost function, which Lasso Regression tries to minimize.
  • Bottom axis (x-axis): represents the value of the lambda (λ) parameter, which controls the strength of the L1 penalty in the cost function.
  • Green to orange curve: This curve depicts how the cost function (y-axis) changes with increasing lambda (x-axis). As lambda increases (moving to the right on the x-axis), the curve transitions from green to orange. This represents the cost function value going up (potentially due to a higher RSS term) as the L1 penalty becomes stronger (forcing more coefficients to zero).

What is lasso regression?

The Lasso Regression, a regression method based on Least Absolute Shrinkage and Selection Operator is quite an important technique in regression analysis for selecting the variables and regularization. It gets rid of irrelevant data features that help to prevent overfitting and features with weak influence become more cleanly identifiable because of shrinking the coefficients toward zero.

In this guide, we will understand core concepts of lasso regression as well as how it works to mitigate overfitting.

What is lasso regression?

  • Understanding Lasso Regression
  • Bias-Variance Tradeoff in Lasso Regression
  • How Does Linear Regression works?
  • When to use Lasso Regression
  • Implementation of Lasso Regression
  • Best Practices for Implementing Lasso Regression
  • Advantages of Lasso Regression
  • Disadvantages of Lasso Regression

Similar Reads

Understanding Lasso Regression

Lasso (Least Absolute Shrinkage and Selection Operator) regression typically belongs to regularization techniques category, which is usually applied to avoid overfitting. Lasso Regression enhance the linear regression concept by making use of a regularization process in the standard regression equation. Linear Regression operates by minimizing the sum of squared discrepancies between the observed and predicted values by fitting a line (or, in higher dimensions, a plane or hyperplane) to the data points. However, multicollinearity a condition in which features have a strong correlation with one another occurs in real-words datasets. This is when the regularization approach of Lasso Regression comes in handy. Regularization, in simple term add penalty term to model, preventing it from overfitting....

Bias-Variance Tradeoff in Lasso Regression

The balance between bias (error resulting from oversimplified assumptions in the model) and variance (error resulting from sensitivity to little variations in the training data) is known as the bias-variance tradeoff.While implementing lasso regression, the penalty term (L1 regularization) helps to significantly lowers the variance of the model by decreasing the coefficients of less significant features towards zero. By doing this, overfitting may be avoided. Hence, the model identifies noise in the training set rather than the underlying patterns. However, as the model may become overly simplistic and unable to represent the true underlying relationships in the data, raising the regularization strength to reduce variance may also increase bias....

How Does Lasso Regression works?

Lasso regression is fundamentally an extension of linear regression. The goal of traditional linear regression is to minimize the sum of squared differences between the observed and predicted values in order to determine the line that best fits the data points. But the complexity of real-world data is not taken into account by linear regression, particularly when there are many factors. 1. Ordinary Least Squares (OLS) Regression: Lasso regression is very useful in this situation because adding a penalty term In lasso regression, minimize the sum of squared differences. The predictors’ coefficients’ absolute values serve as the basis for this penalty. The formula for OLS is:...

When to use Lasso Regression

When working with high-dimensional datasets that contain a large number of features some of which may be redundant or irrelevant, lasso regression is very helpful. Moreover, we can use lasso regression in following situations:...

Implementation of Lasso Regression

Lasso Regression can be implemented using various tools, like Python and R. Python offers a rich ecosystem of libraries for machine learning, commonly used is scikit-learn. Scikit-learn provides a user-friendly interface for executing Lasso Regression. Similar to Python, R also offers package for implementing Lasso Regression which is glmnet package. These tools offer convinient functions for data preprocessing, hyperparameter adjustment, and model evaluation for executing Lasso regression. You are free to select the tool that best suits your demands and level of programming language competence based on your preferences and unique requirements....

Best Practices for Implementing Lasso Regression

Dealing with Multicollinearity: As Lasso struggles to handle multicollinear features, make sure all of the features are multicollinear. Feature Classification: To reduce dimensionality, group features that are highly connected or take into account methods like Principal Component Analysis (PCA). Balance between Variance and Bias: Recognize the balance between variation and bias. Raising the alpha (stronger regularization) decreases variance but increases bias....

Advantages of Lasso Regression

Feature Selection: Lasso regression eliminates the need to manually select the most relevant features, hence, the developed regression model becomes simpler and more explainable.Regularization: Lasso constrains large coefficients, so a less biased model is generated, which is robust and general in its predictions.Interpretability: With lasso, models are often sparsity induced, therefore, they are easier to interpret and explain, which is essential in fields like health care and finance.Handles Large Feature Spaces: Lasso lends itself to dealing with high-dimensional data like we have in genomic as well as imaging studies....

Disadvantages of Lasso Regression

Selection Bias: Lasso, might arbitrarily choose one variable in a group of highly correlated variables rather than the other, thereby yielding a biased model in the end.Sensitive to Scale: Lasso is demanding in the respect that features of different orders have a tendency to affect the regularization line and the model’s precision.Impact of Outliers: Lasso can be easily affected by the outliers in the given data, resulting into the overfitting of the coefficients.Model Instability: In the environment of multiple correlated variables the lasso’s selection of variable may be unstable, which results in different variable subsets each time in tiny data change.Tuning Parameter Selection: Analyzing different λ (alpha) values may be problematic and maybe solved by cross-validation....

Conclusion

In conclusion, Lasso regression is one of the best splendid techniques of machine learning and statistics to build up models concisely and to handle high-dimensional data. Through introducing penalty terms to large coefficients, Lasso regulation adds the sparsity nature of the selection procedure in features. Identifying its sphere of influence and boundaries is of great value for the development of this approach in various fields of use. In the face of vast feature data, Lasso regression can be quite useful as it adds to the effectiveness of a model and its interpretability....