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Neural Network Training (Part 3): Gradient Calculation

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Uploaded by on Aug 15, 2011

In this video we will see how to calculate the gradients of a neural network. The gradients are the individual error for each of the weights in the neural network. In the next video we will see how these gradients can be used to modify the weights of the neural network.

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  • calculus great im fucked

  • @Patterion

    Hey yeah thanks, i had allready figured it out.

    Seems like a lot of neural net- teachers assume u know the derivative of the sigmoidfunction by heart or something :p

    thanx !

  • @00YURIN00

    It actually is not a derivative of constant, but derivative of the transfer (sigmoid) function then evaluated with the 1.13 constant as parameter for x.

    That is:

    f=1/(1+e^(-x)) =>

    f'=(e^x)/[e^(2x)+2e^(x)+1] =>

    f'(1.13)=0.1845 and then

    d=0.25*0.1845=0.046.

    f is sigmoid function and f' is its derivative.

    The 1.13 is actually 1.1278 so that's why 0.046 instead of 0.045.

  • doesn't the derivative of a constant equal zero ?

    i don't get how u get to the 0.045 ... :s

  • Really great tutorials!

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