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The cost function code return opposite sign #76

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SendToSpace opened this issue Sep 13, 2019 · 5 comments
Open

The cost function code return opposite sign #76

SendToSpace opened this issue Sep 13, 2019 · 5 comments

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@SendToSpace
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#Take the error when label=1
class1_cost = -labels*np.log(predictions)

#Take the error when label=0
class2_cost = (1-labels)*np.log(1-predictions)

#Take the sum of both costs
cost = class1_cost + class2_cost

In this code, it seem like class1 return positive cost and class2 return negative cost, wouldn't they cancel when added?

@iandanforth
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If the labels can only be 1 or 0, one of the costs will always be 0.

-0 * anything = 0

Or

1-1 * anything = 0

@SendToSpace
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Author

What I mean was, when label is 0,
(1-0)log(1-p) will give negative cost, should be (label-1)log(1-p), for positive cost, or I could be missing a point here

@iandanforth
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@SendToSpace You're correct. The - sign got moved inside the parens in the equation just above the code as well.

@bfortuner
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Owner

Nice catch if you have time for a pr that would be awesome!

@Chandu-4444
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Hey @bfortuner, Can I make a PR for this? I'm just a beginner wanted to start contributing ot Open Source.

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4 participants