From 9e9b9990bb7fd4741ce3cefc4db0d289c7201da9 Mon Sep 17 00:00:00 2001
From: neingeist <neingeist@bl0rg.net>
Date: Wed, 15 Oct 2014 19:54:07 +0200
Subject: [PATCH] Compute the gradient for regularized logistic regression

---
 ex2/costFunctionReg.m | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/ex2/costFunctionReg.m b/ex2/costFunctionReg.m
index deaae32..572bebf 100644
--- a/ex2/costFunctionReg.m
+++ b/ex2/costFunctionReg.m
@@ -20,6 +20,10 @@ grad = zeros(size(theta));
 J = 1/m * (-y'*log(sigmoid(X*theta)) - (1-y)'*log(1-sigmoid(X*theta))) ...
     + lambda/(2*m) * theta(2:end)' * theta(2:end);
 
+regularization_term = ...
+  lambda/m * (theta .* prepad(ones(length(theta)-1, 1), length(theta), 0));
+grad = 1/m * X' * (sigmoid(X*theta) - y) + regularization_term;
+
 % =============================================================
 
 end