Andrew Ng机器学习笔记#3

                                     Logistic regression

 

1. Hypothesis function and definition:

 

 

Therefore, the final form of the hypothesis function shall look like this:

   

   2. Decision boundary:

 

 

     3.Cost function:

 

 

 

     4.Gradient descent：

 

 

 

Notice that this is exactly the same as that of the linear regression.

 

 

This vectorized implementation is very useful and convenient to express in Matlab & octave.

 

   5.Multiclass classification: