%% Initialization
clear ; close all; clc

%% Load Data
%  The first two columns contains the exam scores and the third column
%  contains the label.

data = http://www.mamicode.com/load(‘ex2data1.txt‘);>

function [theta, J_history] = gredientDescent(X,y,alpha,iteration);
 
  [m,n]=size(X);
  theta = zeros(n,1);
  for(i= 1:iteration)
     [J,grad] = costFunction(theta,X,y);
     J_history(i) = J;
     theta = theta-X‘*(sigmoid(X*theta)-y)*alpha/m;
  endfor 
  
endfunction


function [J, grad] = costFunction(theta, X, y)
m = length(y); 
J = 0;
grad = zeros(size(theta));

tmp=ones(m,1);
h = sigmoid(X*theta);
h1=log(h);
h2=log(tmp-h);

y2=tmp-y;

J=(y‘*h1+y2‘*h2)/(-m);

grad=(X‘*(h-y))/m;
end