# Questions tagged [cost-function]

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### Andrew Ngs Class - Why Did He Change up the Cost Function?

I am taking Andrew Ng's Machine Learning Intro class. Looks like he changed the cost function without any explanation in the second week. Specifically: He no longer squares each deviation between the ...
17 views

### Theano gradient descent and cost function issue

Sorry but can anyone point out whats wrong with this code? ...
47 views

I am not a math expert but have a basic understanding of linear algebra, calculus and probability and I understand the math behind back propagation. Currently I am trying to learn about policy ...
147 views

### Policy gradient vs cost function

I was working with continuous system RL and obviously stumbled across this Policy Gradient. I want to know is this something like cost function for RL? It kinda gives that impression considering we ...
58 views

### Neural network cost is constant never changing during training

I am trying to build a binary classifier to predict a pulsar star with Single Hidden layer Neural Network. But the cost on training dataset after almost 100 iterations has no change, following is the ...
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### Question of using gradient descent instead of calculus. I checked previous questions there are still points to clarify

First of all I checked http://stats.stackexchange.com/questions/23128/solving-for-regression-parameters-in-closed-form-vs-gradient-descent, http://stackoverflow.com/questions/26804656/why-do-we-use-...
27 views

### Reason behind the sum of rate factors for calculating cost function derivative

Suppose we have a network of neurons like below: We make a little change in weight w[l][j][k] on our network, and it can make change on our cost function from ...
74 views

### Minimum cost is not zero when calculating cross-entropy on soft labels

I am training a neural network using batches of soft labels, e.g. y = [[0.00, 0.25, 0.25, 0.50], ... [0.75, 0.00, 0.20, 0.05]] However, as ...
29 views

Problem I am now taking Andrew Ng's deep learning course on Coursera. Everything is great but when it comes to RNN, I sometimes feel confused. Here is a question about RNN (or more specifically, the ...
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### logistic regression algorithm fails to work

I'm trying to code my own logistic regression algorithm using Andrew NG's machine learning using Octave. lectures. So what I did was make a csv file, the first row being some parameter and the second ...
195 views

### Derivation of the cross-entropy equation in Michael Nielsen's book

I am reading the book http://neuralnetworksanddeeplearning.com/chap3.html by Michael Nielsen. So this is a question mostly for the people familiar with the book and understanding the material. In the ...
1k views

### Gradient Descent in logistic regression

Logistic and Linear Regression have different cost functions. But I don't get how the gradient descent in logistic regression is the same as Linear Regression. We get the Gradient Descent formula by ...
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22k views

### Python implementation of cost function in logistic regression: why dot multiplication in one expression but element-wise multiplication in another

I have a very basic question which relates to Python, numpy and multiplication of matrices in the setting of logistic regression. First, let me apologise for not using math notation. I am confused ...
865 views

### Is cross-entropy a good cost function if I'm interested in the probabilities of a sample belonging to a certain class?

I'm training a neural network that, for each of six classes, tries to predict the probability that a sample belongs to it. After that, I want to use these probabilities as fractions of the sample ...
93 views

### Any Neural Network implementations that allow for a cost function of more than just the network output?

I have an application of a straightforward MLP, for which the cost function is a function of both the network output, in addition to another value calculated from the network weights (actually the ...