无监督学习，进行线性拟合梯度下降，选择thet-This first exercise will give you practice with linear regression. These exercises have been extensively tested with Matlab, but they should also work in Octave, which has been called a　free version of Matlab.　If you are using Octave, be sure to install the Image package as well (available for Windows as an option in the installer, and available for Linux　Octave-Forge ).