Building a Neural Network from Scratch in Python

We're gonna use python to build a simple 3-layer feedforward neural network to predict the next number in a sequence. We'll go over the concepts involved, the theory, and the applications. Lead by: Siraj Raval of Sirajology

[googlr]

from basic neural network to tensorflow to rnn to cnn. this helps a lot! thanks!

[rabikhan]

People talking shit about Siraj, listen, nobody is perfect. Have you ever programmed? Errors come and go and the process takes time. It's heard to stand there in front of an audience and do live programming, it's just hard, imagine it. He tried to explain and his audience was not noobs. He at least tried, what you didn't so stay cool and study the basics again, come back here and see the difference. He is an awesome teacher, and he is an inspiration to a lot of people and he is the teacher so instead of pointing negatives, point positives. That's what you're supposed to do when learning.

[mitkosokolov]

Hi, is there any example of Zigbee mesh network ?

[markvarney]

Far better to learn Neural Networks from Sentdex.He has a channel, and also a website.He gives a very good and simple explanation for everything that he does.

[uttam]

line 43 there are 3 opening brackets but only 2 closing brackets, yet his code runs...this is amazing.

[akshaylakhe]

after breaking my head for entire day behind logic of dot product of synapses and input and the order they should be multiplied i really dont know whether i am right or wrong but what i understand is when initializing dimensions for synapses suppose for layer 1 i.e syn0, dimensions should be (4, 3).It make sense to me as(4, 3) as for each row denoting each neuron in layer 2 having 3 columns as 3 input features but it does not output single value at the end of all layes but now i realizes(thank you i got it now ) vice versa is right because if finalizes to single value. Thank you SIRAJ indirectly affecting millions of amatures like me... ; >)

[novicetech]

Maybe I missed something but I'm wondering why there is no backpropagation function for an L1_error like there is for L2_error (line 40). I'm new to both Python and Neural Networks but that seems odd to me. Would you (or anyone) mind helping me understand why backpropagation is not required for L1? Thanks

[anteconfig]

python doesn't compile.. Am I missing something?

[stuartallen]

Hey I followed along recreating the python program as he went. I double checked to make sure we typed the same things. However, my error goes down a lot slower than his. Why might this be?

[anupkodlekere]

All this is cool, but can someone explain what does this actually mean? Like what does the x and y array represent?

[lakaiguy]

How do you draw the node/layers picture based off the input and output matrices?

[jonathanplasky]

Awesome Video! Fun and exciting and yes not perfect.

[richardfredlund]

RE: the first example. This is great. The code compiles, and I get the same numbers. What I'm a bit confused about is why there is no learning rate and is this applying back propagation?

[FilipeRebollo]

Why deriv is x*(1-x)? Filipe from brazilll

[xRapidFirex]

sigmoid functions take a number and turn it into a probability? That sounds like nonsense, I don't understand, the probability of what? If my input to a sigmoid function is 500, what does the result represent? A probability? of what?

[Therealbighustle]

I'm learning more on this I'm just getting started I've learned alot if python

[aryehpechet]

After training how do you predict the output value given the next input?

[Shubhankar.Banerjee]

Every time I try to compile the code in python, it throws an error. Please help

[hassanmehdi]

i feel like he doesn't give good explanation for using dot and transpose. i took matrix algebra but didn't have a focus on implementation and would love an idea of why and how to apply those concepts

[els]

if I change the x matrix, the output has big error, can anyone solve the problem?