How ANN (Artificial Neural Networks) Algorithm Works

In this video I explain the propagation of values inside the neural network algorithm.
The backpropagation, which is used to train the network, is not discussed in this video.
The weights of the connections were defined randomly, but the results of the propagation are correct. We used three different activation functions only to show that in the neural network it is possible to define more than one type of activation function.

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#ann #deep-learning #machine-learning

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All About Artificial Neural Networks – What, Why, and How?

If you are interested in Artificial Intelligence, chances are that you must have heard about Artificial Neural Networks (ANN), and Deep Neural Networks (DNN). This article is about ANN.

The boom in the field of artificial intelligence may have come recently, but the idea is old. The term AI was coined way back in 1956. Its revival though in the 21st century can be traced to 2012 when ImageNet challenge. Before this, AI was known as neural networks or expert systems.

At the foundation of AI are the networks of artificial neurons, the same as the cells of a biological brain. Just like every neuron can be triggered by other neurons in a brain, AI works similarly through ANNs. Let’s know more about them.

Artificial Neural Networks – Borrowing from human anatomy
Popularly known as ANN, Artificial Neural Network is basically a computational system, which is inspired by the structure, learning ability, and processing power of a human brain.

ANNs are made of multiple nodes imitating the neurons of the human brain. These neurons are connected by links and also interact with each other. These nodes facilitate the input of data. The structure in ANN is impacted by the flow of information, which changes the neural networks based on the input and output.

A simple, basic-level ANN is a “shallow” neural network that has typically only three layers of neurons, namely:

Input Layer. It accepts the inputs in the model.
Hidden Layer.
Output Layer. It generates predictions.

#artificial neural networks #neural networks #ai #ml #artificial intelligence

Introduction to Artificial Neural Networks for Beginners

Introduction

ANNs (Artificial Neural Network) is at the very core of Deep Learning an advanced version of Machine Learning techniques. ANNs are versatile, adaptive, and scalable, making them appropriate to tackle large datasets and highly complex Machine Learning tasks such as image classification (e.g., Google Images), speech recognition (e.g., Apple’s Siri), video recommendation (e.g., YouTube), or analyzing sentiments among customers (e.g. Twitter Sentiment Analyzer).

ANN was first introduced in 1943 by the neurophysiologist Warren McCulloch and the mathematician Walter Pitts. However, ANN had its ups and downs. Post-1960 there was a drop in interest and excitement among researchers w.r.t neural networks with the advancement of Support Vector Machines and other powerful Machine Learning techniques that produced better accuracy and had a stronger theoretical foundation. Neural networks were complex and required tremendous computation power and time to train. However post 1990, the advancement in the field of computation (refer to Moore’s law) followed by the production of powerful GPU cards brought some interest back.

#data-science #neural-networks #machine-learning #artificial-neural-network #artificial-intelligence

No Code introduction to Neural Networks

The simple architecture explained

Neural networks have been around for a long time, being developed in the 1960s as a way to simulate neural activity for the development of artificial intelligence systems. However, since then they have developed into a useful analytical tool often used in replace of, or in conjunction with, standard statistical models such as regression or classification as they can be used to predict or more a specific output. The main difference, and advantage, in this regard is that neural networks make no initial assumptions as to the form of the relationship or distribution that underlies the data, meaning they can be more flexible and capture non-standard and non-linear relationships between input and output variables, making them incredibly valuable in todays data rich environment.

In this sense, their use has took over the past decade or so, with the fall in costs and increase in ability of general computing power, the rise of large datasets allowing these models to be trained, and the development of frameworks such as TensforFlow and Keras that have allowed people with sufficient hardware (in some cases this is no longer even an requirement through cloud computing), the correct data and an understanding of a given coding language to implement them. This article therefore seeks to be provide a no code introduction to their architecture and how they work so that their implementation and benefits can be better understood.

Firstly, the way these models work is that there is an input layer, one or more hidden layers and an output layer, each of which are connected by layers of synaptic weights¹. The input layer (X) is used to take in scaled values of the input, usually within a standardised range of 0–1. The hidden layers (Z) are then used to define the relationship between the input and output using weights and activation functions. The output layer (Y) then transforms the results from the hidden layers into the predicted values, often also scaled to be within 0–1. The synaptic weights (W) connecting these layers are used in model training to determine the weights assigned to each input and prediction in order to get the best model fit. Visually, this is represented as:

#machine-learning #python #neural-networks #tensorflow #neural-network-algorithm #no code introduction to neural networks

A financial neural network for quants

Artificial intelligence (AI) is continuously becoming an integral part of what we do nowadays, from the suggestions of the YouTube videos we ought to watch, to the algorithms running our high frequency trading in the Wall Street. Indeed Google algorithms know what we prefer, better than what we want. That was according to the Twitter CEO and founder — Jack Dorsey. This would not be mentioned if it were not for pattern recognition and classification, which are the main underlying…

#artificial-intelligence #finance #artificial-neural-network #data-science #algorithms #algorithms

Comparison between Logistic Regression and Neural networks

I recently learned about logistic regression and feed forward neural networks and how either of them can be used for classification. What bugged me was what was the difference and why and when do we prefer one over the other. So, I decided to do a comparison between the two techniques of classification theoretically as well as by trying to solve the problem of classifying digits from the MNIST dataset using both the methods. In this article, I will try to present this comparison and I hope this might be useful for people trying their hands in Machine Learning.

Source

The code that I will be using in this article are the ones used in the tutorials by Jovian.ml and freeCodeCamp on YouTube. The link has been provided in the references below.

Problem Statement

Given a handwritten digit, the model should be able to tell whether the digit is a 0,1,2,3,4,5,6,7,8 or 9.

We will use the MNIST database which provides a large database of handwritten digits to train and test our model and eventually our model will be able to classify any handwritten digit as 0,1,2,3,4,5,6,7,8 or 9. It consists of 28px by 28px grayscale images of handwritten digits (0 to 9), along with labels for each image indicating which digit it represents. We will learn how to use this dataset, fetch all the data once we look at the code.

Let us have a look at a few samples from the MNIST dataset.

Examples of handwritten digits from the MNIST dataset

Now that we have a clear idea about the problem statement and the data-source we are going to use, let’s look at the fundamental concepts using which we will attempt to classify the digits.

You can ignore these basics and jump straight to the code if you are already aware of the fundamentals of logistic regression and feed forward neural networks.

Logistic Regression

I will not talk about the math at all, you can have a look at the explanation of Logistic Regression provided by Wikipedia to get the essence of the mathematics behind it.

So, Logistic Regression is basically used for classifying objects. It predicts the probability(P(Y=1|X)) of the target variable based on a set of parameters that has been provided to it as input. For example, say you need to say whether an image is of a cat or a dog, then if we model the Logistic Regression to produce the probability of the image being a cat, then if the output provided by the Logistic Regression is close to 1 then essentially it means that Logistic Regression is telling that the image that has been provided to it is that of a cat and if the result is closer to 0, then the prediction is that of a dog.

It is called Logistic Regression because it used the logistic function which is basically a sigmoid function. A sigmoid function takes in a value and produces a value between 0 and 1. Why is this useful ? Because probabilities lie within 0 to 1, hence sigmoid function helps us in producing a probability of the target value for a given input.

The sigmoid/logistic function looks like:

where e is the exponent and **_t _**is the input value to the exponent.

Generally **_t _**is a linear combination of many variables and can be represented as :

The standard logistic function:

NOTE: Logistic Regression is simply a linear method where the predictions produced are passed through the non-linear sigmoid function which essentially renders the predictions independent of the linear combination of inputs.

Neural networks

Artificial Neural Networks are essentially the mimic of the actual neural networks which drive every living organism. They are currently being used for variety of purposes like classification, prediction etc. In Machine Learning terms, why do we have such a craze for Neural Networks ? Because they can approximate any complex function and the proof to this is provided.

What does a neural network look like ? Like this:

ANN with 1 hidden layer, each circle is a neuron. Source: Wikipedia

That picture you see above, we will essentially be implementing that soon. Now, what you see in that image is called a neural network architecture, you can make your own architecture by defining more than one hidden layers, add more number of neurons to the hidden layers etc. Now, there are some different kind of architectures of neural networks currently being used by researchers like Feed Forward Neural Networks, Convolutional Neural Networks, Recurrent Neural Networks etc.

In this article we will be using the Feed Forward Neural Network as its simple to understand for people like me who are just getting into the field of machine learning.

Feed Forward Neural Networks

Let us talk about perceptron a bit. This is a neural network unit created by Frank Rosenblatt in 1957 which can tell you to which class an input belongs to. It is a type of linear classifier.

What do you mean by linearly separable data ?

As you can see in image A that with one single line( which can be represented by a linear equation) we can separate the blue and green dots, hence this data is called linearly classifiable.

And what does a non-linearly separable data look like ?

Like the one in **image B. **We can see that the red and green dots cannot be separated by a single line but a function representing a circle is needed to separate them. As the separation cannot be done by a linear function, this is a non-linearly separable data.

Why do we need to know about linear/non-linear separable data ?

Because a single perceptron which looks like the diagram below is only capable of classifying linearly separable data, so we need feed forward networks which is also known as the multi-layer perceptron and is capable of learning non-linear functions.

A single layer perceptron and-multi-layer-perceptrons-the-artificial-neuron-at-the-core-of-deep-learning/)

A Feed forward neural network/ multi layer perceptron:

A multi layer perceptron(Feed Forward Neural Network). Source: missinglink.ai

I get all of this, but how does the network learn to classify ?

Well we must be thinking of this now, so how these networks learn comes from the perceptron learning rule which states that a perceptron will learn the relation between the input parameters and the target variable by playing around (adjusting ) the weights which is associated with each input. If the weighted sum of the inputs crosses a particular thereshold which is custom, then the neuron produces a true else it produces a false value. Now, when we combine a number of perceptrons thereby forming the Feed forward neural network, then each neuron produces a value and all perceptrons together are able to produce an output used for classification.

Now that was a lot of theory and concepts !

I have tried to shorten and simplify the most fundamental concepts, if you are still unclear, that’s perfectly fine. I am sure your doubts will get answered once we start the code walk-through as looking at each of these concepts in action shall help you to understand what’s really going on. I have also provided the references which have helped me understand the concepts to write this article, please go through them for further understanding.

Let’s start the most interesting part, the code walk-through!

Importing Libraries

We will be working with the MNIST dataset for this article. torchvision library provides a number of utilities for playing around with image data and we will be using some of them as we go along in our code.

#logistic-regression #artificial-intelligence #machine-learning #classification-algorithms #artificial-neural-network #algorithms