University:
Stanford University
Course:
CS229 | Machine Learning
Academic year:

2023
Views:

65

Pages:

2
Author:

anon

A Comprehensive Guide to Understanding the Cost Function in Linear Regression When modeling the relationship between two variables, linear regression is a potent method used in data science and machine learning. A straight line with the best fit to the training set of data is what linear regression seeks to identify. By determining the parameters of the linear regression model with the best values, this is accomplished. As it assesses the discrepancy between the predicted values of the target variable and their actual real values, the cost function is a crucial component of this procedure. We'll explore the cost function in greater detail and develop a better understanding of its purpose in this post. What does the cost function in linear regression look like? The difference between the model's predictions and the target variable's actual true values is quantified by the cost function in linear regression. The objective of linear regression is to identify the model parameter values that minimize the cost function. The cost function is a formula that expresses the discrepancy between the predicted values of the model and the actual true values. It's used to evaluate how well the linear regression model fits the practice data. Because it affects how well the model fits the training data, the cost function is an essential component of the linear regression model. When the cost function has a low value, the model accurately represents the training set of data, and when it has a large value, the model does not accurately represent the training set. To ensure that the model fits the training data as closely as possible, the cost function is employed to optimize the model's parameter values. Cost-based pricing and the Simplified Model We will first examine a condensed version of the linear regression model in order to better comprehend the cost function. 𝑓𝑤(𝑥) = 𝑤 · 𝑥, where w is the model parameter and x is the input, will be used to represent this streamlined model. Finding w's value at which the cost function J is minimized is the objective of this simple model (w). The difference between the target variable's actual real values and the model's predictions is quantified by the cost function J(w). The cost function J(w) in this streamlined form resembles the original cost function, with the exception that J(w) is now a function of simply w and not w and b. Finding w's value at which J is minimized is the aim of this streamlined model (w). The Cost Function as a Visualization By putting the cost function J(w) and the model 𝑓𝑤(𝑥) = 𝑤 · 𝑥 side by side, we may better grasp the cost function. When w is fixed, f(w) only depends on x, meaning that the estimated value of the target variable is based on the value of the input x. On the other hand, the cost function J(w) is a function of w, and w determines the angle of the line defined by f. (w). The parameter w affects how much is defined by J(w). We may visualize their relationship by plotting these functions side by side. For instance, as w increases, the slope of the line defined by f(w) similarly rises, causing the gap between the predicted values of the target variable and their actual real values to widen. Due to this, the cost function J has a greater value (w).