For logistic regression The cost function is different than the squared error cost function (used for linear regression). Then how come when computing the gradient descent of logistic regression cost function, the gradient descent of linear regression cost function is calculated. I understand the f(…

The reason the update rule looks identical is due to how the Chain Rule interacts with the Sigmoid function. When we calculate the derivative of the Logistic Cost function d/dwj J(w, b), we break it down into three parts: How the Cost changes with respect to the Prediction (f). How the Predic…

Thank you @sanjaypsachdev for the clarification and reminding me the concept of chain rule in derivatives.

Thank you @paulinpaloalto for further reference.

Week 3: Gradient Descent Implementation

Course Q&A Machine Learning Specialization Supervised ML: Regression and Classification

paulinpaloalto March 28, 2026, 5:32pm 3

Here’s another historical thread that shows the calculation of the derivatives in the Logistic Regression/sigmoid/cross entropy loss case.

Topic		Replies	Views
Derivative of "Simplified Cost Function" Supervised ML: Regression and Classification week-module-3	1	600	March 19, 2023
How to get the derivatives of the logistic cost/loss function [TEACHING STAFF] Supervised ML: Regression and Classification week-module-3	18	4297	May 9, 2024
Why the linear regression and classification have identical Gradient Function? Supervised ML: Regression and Classification week-module-2	5	742	February 11, 2023
What's the usage of J(w,b) for logistic regression? Supervised ML: Regression and Classification week-module-3	18	799	June 9, 2024
Why logistic regression is not used to calculate gradient descent Supervised ML: Regression and Classification week-module-3	8	404	May 8, 2024

Week 3: Gradient Descent Implementation

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