Mercurial > hg > tvii
view tvii/logistic_regression.py @ 13:8cb116d63a78
[notes]
author | Jeff Hammel <k0scist@gmail.com> |
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date | Sun, 03 Sep 2017 12:04:00 -0700 |
parents | 8d25213513b4 |
children | b95fe82ac9ce |
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""" z = w'x + b a = sigmoid(z) L(a,y) = -(y*log(a) + (1-y)*log(1-a)) [| | | ] X = [x1 x2 x3] [| | | ] [z1 z2 z3 .. zm] = w'*X + [b b b b ] = [w'*x1+b + w'*x2+b ...] """ import numpy as np def logistic_regression(_): """the slow way""" J = 0 dw1 =0 dw2=0 db=0 def logistic_regression(nx): dw = np.zeros(nx) # TODO # z = np.dot(wT, x) + b # "boradcasting raise NotImplementedError('TODO') # derivativs: # dz1 = a1 - y1 ; dz2 = a2 - y2 ; .... # dZ = [ dz1 dz2 ... dzm ] # Z = w'X + b = np.dot(w', X) + b # A sigmoid(Z) #dZ = A - Y #dw = (1./m)*X*dZ' #db = (1./m)*np.sum(dZ) # w -= alpha*dw # b -= alpha*db