What is Logistic Regression: A Detailed Guide

Are you just a beginner in the field of data science? If so, you may be learning about various tools and methods of the trade. One such essential and valuable thing to learn in the data science and analytics field is logistic regression. It is one specific sort of analysis that data scientists leverage.

But what is this logistic regression exactly? What does it entail? Let’s find out in this guide.

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What Is Logistic Regression?

Logistic regression is a widely-used statistical analytic technique that leverages previous analyses of an array of data to forecast binary conclusions, like yes or no. 

In simple terms, logistic regression algorithms analyze the association between single or multiple independent factors to predict the dependent variable. 

For example, it can forecast whether a student will be admitted to a specific university. These binary results provide an easy choice between two different variables.

Also read: Artificial Intelligence: A Beginner’s Guide

Logistic Regression Assumptions

While logistic regression appears like a reasonably simple technique to learn & execute, there are plenty of limits concerning its application. For example, it is only applicable to huge datasets. For this machine-learning approach to work, other assumptions must also be made about the dataset. 

This includes the following:

• The objective must be reflected in the dependent variable’s factor level 1. 
• The independent variables must have minimal or no multicollinearity, meaning that they are completely independent of one another. 
• A binary logistic equation demands that the dependent variable be binary.
• Non-meaningful variables could result in errors. Only incorporate the factors that are required and might demonstrate a correlation.
• The independent variables and the log odds are correlated linearly.

You might believe that the equation can’t be applied to practical issues because so many presumptions must be made. Nevertheless, this equation has a wide range of medical applications, is incredibly well-liked among data scientists, and uses its superpower to benefit people worldwide.

Also read: Real-World Applications of Machine Learning in Finance Industry

Types of Logistic Regression

Till now, we primarily focused on the binary logistic regression type, which has only two potential categories or outcomes. Logistic regression comes in three types, including the one we’re all familiar with.

Logistic regression is of three types, including the following: 

Binary Logistic Regression: 

• This is a commonly-used statistical approach to foresee a correlation. 
• Not just any correlation, but the one between the independent variable (x) and the dependent variable (y) when the latter (y) is binary in nature. 
• For instance, the outcome can be Yes/No, Success/Failure, True/False, or 0/1. 

Multinomial Logistic Regression: 

This type is leveraged when there are two or multiple distinct results, i.e., more levels of one categorical dependent variable. Except for the fact that there can be over two potential outcomes here, it is quite equivalent to logistic regression. 

Consider the scenario where you wish to foretell the most popular mode of transportation in 2030. The dependent variable will correspond to the mode of transportation, with bike, tram, bus, and train as possible outputs.’

Ordinal Logistic Regression: 

Ordinal logistic regression is leveraged when the dependent variable (y) is ordinal (ordered). Not only does the dependent variable comes with a meaningful and valuable hierarchy, but also with over two levels. Do you know what these variables may entail? 

Let’s say t-shirt sizes from XL to XS, test results like Good, Bad, Average, Excellent, or survey responses like Neutral, Disagree, and Agree. 

No matter the kind of logistic regression, the procedure for training the logistic regression model is always the same.

Logistic Regression Training

Why train the logistic regression model? What is the benefit of doing so? Well, it establishes the ideal weights for your linear model. Also, it does so within the logistic regression. When it comes to machine learning, programmers determine the ideal weights using cost function optimization. 

Cost Function

The goal the method attempts to accomplish is formalized as the cost function J(). The objective of logistic regression is to lower or minimize the subsequent cost function equation, which is known as LogLoss (or Cross-Entropy):

All you have to do is comprehend the underlying ideas:

• The cost function determines the average discrepancy between expected and actual class membership. This results from the precise weight choices we made for our linear model.
• In addition to large errors, the cost function penalizes overconfident errors (too near to 0 or 1). This ensures that all of our forecasts fall solely between 0 and 1.

So how can we create a model that makes accurate predictions and has a low value for our cost function? By using Gradient descent!

Gradient Descent 

Gradient descent is a technique for altering weights depending on the loss function for every point of data. The LogLoss cost function computation is done at every data input and output point. 

• The cost functions’ slope at every location is obtained by taking a partial derivative of the bias and the weight. 
• Gradient descent adjusts the set of weights values and the bias depending on the slope, iterating the loop of training over the updated values. 
• Gradient descent is used to lower the cost function until a minimum error is attained, and it is no longer possible to do so.
• By altering the learning rate, we can update the rate at which we arrive at the ideal minimum.

In contrast to low learning rates, high learning rates cause weights to change or alter more quickly. The amount of learning rate is subject to trade-off. 

If you set the weights too high or too low, your model can take an eternity to find the best set. Also, it’s possible that you won’t find the best set at all since the model won’t converge.

Also read: The Future of AI and ML

Benefits of Logistic Regression 

The following are a few benefits of logistic regression analysis that helps data science professionals to carry out their day-to-day work: 

• Simple & Easy To Learn: This supervised learning model is far simpler to understand than other ML models. After all, models are much more helpful in the context of Machine Learning because they are mathematically simpler than other ML models. So, no matter if you lack extensive ML experience, you can still create, train, and deploy effective ML models using logistic regression. 
• Quick Processing: Large data sets are processed quickly because they demand less processing power and memory than smaller ones. They are, therefore, perfect for programmers seeking immediate gains while working on challenging ML tasks. 
• Visibility: Compared to other data analysis methodologies, the logistic regression analysis provides coders with a clearer view of internal software operations. As the complexity of the equation’s computations decreases, troubleshooting gets simpler.

Logistic Regression Tools 

Logistic regression computations were a tedious and time-consuming operation before the arrival of modern computers. Today, logistic regression capabilities are crucial to contemporary statistical analytics systems like SAS and SPSS.

Additionally, there are many ways to do logistic regression and incorporate the outcomes into other algorithms using data science programming languages and frameworks based on Python and R. There are many various tools and approaches for undertaking logistic regression analysis on top of Excel.

When it comes to serious data science democratization efforts, managers must consider various data management and data preparation technologies. For instance, organizing larger data collections for logistic regression can be aided by data warehouses and data lakes. 

One can use the best data catalog tools to mitigate the usability or quality issues related to logistic regression. Analytics leaders can develop the necessary safeguards using data science platforms, making it easier for logistic regression to be used more widely throughout the company.

Conclusion: Getting Started With Logistic Regression! 

The end is the beginning! While the article ends here, your actual learning journey begins! Enroll in one of the best data science courses to learn every possible aspect of logistic regression. 

These courses can aid you in many ways, from delving into the theories and methods in-depth to making practical applications. 

Additionally, you will get to put all of your learned information and abilities to use as you create an ML model, assemble a resume-worthy portfolio, catch the interest of potential employers, and secure your desired position!  

Get started today! 

Relevant Programs via upGrad:

• Master of Science in Machine Learning & AI (Liverpool John Moores University)
• Executive Diploma in Machine Learning & AI (IIT Bangalore)

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