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Linear regression with one varia

Linear regression with one varia

作者: spraysss | 来源:发表于2020-01-27 13:20 被阅读0次

    Housing Prices

    Hypothesis:

    h_{\theta}(x)=\theta_0+\theta_1x

    Parameters:

    \theta_0\theta_1

    Cost function:

    Squared error
    J(\theta_0,\theta_1)=\frac{1}{2m}\sum_{i=1}^{m}(h_\theta(x^i)-y^i)^2

    Goal

    Min J(\theta_0,\theta_1)

    Gradient descent

    • start with some \theta_0,\theta_1
    • keep changing \theta_0,\theta_1 to reduce J(\theta_0,\theta_1) until we hopefully end up at a minimum

    Gradient descent algorithm

    repeat until convergence {
    \space \theta_j:=\theta_j-\alpha\frac{\partial}{\partial\theta_j}J(\theta_0,\theta_1) (for \space j=0 \space and \space j=1)
    }
    Note : the Correct way is simultaneous update

    • temp0:=\theta_0:=\theta_0-\alpha\frac{\partial}{\partial\theta_0}J(\theta_0,\theta_1)
    • temp1:=\theta_1:=\theta_1-\alpha\frac{\partial}{\partial\theta_1}J(\theta_0,\theta_1)
    • \theta_0:=temp0
    • \theta_1:=temp1

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