Lecture Note
University
Stanford UniversityCourse
CS229 | Machine LearningPages
2
Academic year
2023
anon
Views
22
A Comprehensive Guide to Understanding the Cost Function inLinear Regression When modeling the relationship between two variables, linear regression is a potent methodused in data science and machine learning. A straight line with the best ﬁt to the training setof data is what linear regression seeks to identify. By determining the parameters of thelinear regression model with the best values, this is accomplished. As it assesses thediscrepancy 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 ingreater 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 isquantiﬁed by the cost function in linear regression. The objective of linear regression is toidentify the model parameter values that minimize the cost function. The cost function is aformula that expresses the discrepancy between the predicted values of the model and theactual true values. It's used to evaluate how well the linear regression model ﬁts the practicedata. Because it affects how well the model ﬁts the training data, the cost function is an essentialcomponent of the linear regression model. When the cost function has a low value, themodel accurately represents the training set of data, and when it has a large value, the modeldoes not accurately represent the training set. To ensure that the model ﬁts the training dataas closely as possible, the cost function is employed to optimize the model's parametervalues. Cost-based pricing and the Simpliﬁed Model We will ﬁrst examine a condensed version of the linear regression model in order to bettercomprehend the cost function. , where w is the model parameter and x is the 𝑓 𝑤 (𝑥) = 𝑤 · 𝑥 input, will be used to represent this streamlined model. Finding w's value at which the costfunction 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 isquantiﬁed by the cost function J(w). The cost function J(w) in this streamlined formresembles the original cost function, with the exception that J(w) is now a function of simplyw and not w and b. Finding w's value at which J is minimized is the aim of this streamlinedmodel (w). The Cost Function as a Visualization By putting the cost function J(w) and the model side by side, we may better 𝑓 𝑤 (𝑥) = 𝑤 · 𝑥 grasp the cost function. When w is ﬁxed, f(w) only depends on x, meaning that the estimatedvalue of the target variable is based on the value of the input x. On the other hand, the costfunction J(w) is a function of w, and w determines the angle of the line deﬁned by f. (w). Theparameter w affects how much is deﬁned by J(w).
We may visualize their relationship by plotting these functions side by side. For instance, asw increases, the slope of the line deﬁned by f(w) similarly rises, causing the gap between thepredicted values of the target variable and their actual real values to widen. Due to this, thecost function J has a greater value (w).
Understanding the Cost Function in Linear Regression
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