# Questions tagged [derivation]

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### calculating derivative of bias in backpropagation

Looking at the algorithm in wikipedia, we can implement backpropagation by calculating: $$\delta^{L}=\left(f^{L}\right)'\cdot\nabla_{a^{L}}C$$ (where I treat $\left(f^{L}\right)'$ as an $n\times n$ ...
• 101
1 vote
28 views

### How to compute backpropagation gradient according chain rule for using vector/matrix differential?

I have some problems for computing derivative for sum of squares error in backprop neural network. For example, we have a neural network as in picture. For drawing simplicity, i've dropped the sample ...
80 views

### Adding a group specific penalty to binary cross-entropy

I want to implement a custom Keras loss function that consists of plain binary cross-entropy plus a penalty that increases the loss for false negatives from one class (each observation can belong to ...
• 1
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### Understanding the step of SGD for binary classification

I cannot understand the step of SGD for binary classification. For example, we have $y$ - true labels $\in \{0,1\}$ and $p=f_\theta(x)$-predicted labels $\in [0,1]$. Then, the update step of SGD is ...
• 101
47 views

### Batch normalization backpropagation doubts

I have recently studied the batch normalization layer and its backpropagation process, using as my main sources the original paper and this website showing part of the derivation process, but there is ...
62 views

### Loss function for points inside polygon

I am trying to optimize some parameters that used to transform 2d points from a place to another (you may think of that as rotation & translation parameter for simplicity) The parameters are ...
1 vote
105 views

### SVM - Making sense of distance derivation

I am studying the math behind SVM. The following question is about a small but important detail during the SVM derivation. The question Why the distance between the hyperplane $w*x+b=0$ and data ...
• 21
37 views

### Deriving vectorized form of linear regression

We first have the weights of a D dimensional vector $w$ and a D dimensional predictor vector $x$, which are all indexed by $j$. There are $N$ observations, all D dimensional. $t$ is our targets, i.e, ...
• 143
131 views

### Why is it valid to remove a constant factor from the derivative of an error function?

I was reading the book 'Make your own neural network' by Tariq Rashid. In his book, he said: (Note - He's talking about normal feed forward neural networks) The $t_k$ is the target value at node $k$, ...
1 vote
75 views

### How is this score function estimator derived?

In this paper they have this equation, where they use the score function estimator, to estimate the gradient of an expectation. How did they derive this?
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4k views

### Is it valid to use numpy.gradient to find slope of line as well as slope of curve at any point?

what is the difference between slope of the line and slope of the curve? Is it valid to use numpy.gradient to find the slope of the line and slope of the curve at ...
• 1,201
173 views

### 1st order Taylor Series derivative calculation for autoregressive model

I wrote a blog post where I calculated the Taylor Series of an autoregressive function. It is not strictly the Taylor Series, but some variant (I guess). I'm mostly concerned about whether the ...
• 121
1 vote
347 views

### Derivative of Loss wrt bias term

I read this and have an ambiguity. I try to understand well how to calculate the derivative of Loss w.r.t to bias. In this question, we have this definition: ...
156 views

### Maximum Entropy Policy Gradient Derivation

I am reading through the paper on Reinforcement Learning and Control as Probabilistic Inference: Tutorial and Review by Sergey Levine. I am having a difficulty in understanding this part of the ...
1 vote
18 views

### back propagation through time derivation issue

I read several posts about BPTT for RNN, but I am actually a bit confused about one step in the derivation. Given $$h_t=f(b+Wh_{t-1}+Ux_t)$$ when we compute $\frac{\partial h_t}{\partial W}$, does ...
• 151
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### Doubt in Derivation of Backpropagation

I was going through the derivation of backpropagation algorithm provided in this document (adding just for reference). I have doubt at one specific point in this derivation. The derivation goes as ...
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1 vote