Given a waveform that varies in shape over time (see attached) what Neural Network architecture would be best suited to give results with limited training data (less than 100 samples)?
Below is an example representation of the data we would be looking to classify. We have evaluated a 3D CNN model and are currently looking at a LSTM model but both require a large amount of training data to get reasonable results.
It has been mentioned in many places that CNNs are very effective for Image Data compared to ANNs.
What exactly are the differences between CNN and ANN (or) what are the key advantages of CNN over ANN for Image Data.
Key advantages of CNN over ANN are
Learns Spatial Hierarchy of Patterns i.e., Higher Layers of CNN are formed by combining Lower Layers. This helps in identifying the Patterns more effectively than ANN
Translation Invariant: Once the CNN has learned to recognize a pattern in one location, it can recognize it in any other
location. In short, learning (weights) can be reused even if the Image is Rotated or Shifted
All the differences between ANN and CNN are mentioned below.
I have added it as a screenshot as I want to represent the differences in a proper Tabular Format.
I just want to know if a neural network can be trained with a single class of data set. I have a set of data that I want to train a neural network with. After training it, I want to give new data(for testing) to the trained neural network to check if it can recognize it as been similar to the training sample or not.
Is this possible with neural network? If yes, will that be a supervised learning or unsupervised.
I know neural networks can be used for classification if there are multiple classes but I have not seen with a single class before. A good explanation and link to any example will be much appreciated. Thanks
Of course it can be. But in this case it will only recognize this one class that you have trained it with. And depending on the expected output you can measure the similarity to the training data.
An NN, after training, is just a function. For classification problems you can imagine it as a function that takes data as input and returns an integer indicating to which class it belongs to. That being said, if you have only one class that can be represented by an integer value 1, and if training data is not similar to that class, you will get something like 1.555; It will not tel you that it belongs to another class, because you have introduced only one, but it will definitely give you a hint about its similarity.
NNs are considered to be supervised learning, because before training you have to provide both input and target, i. e. the expected output.
If you train a network with only a single class of data then It is popularly known as One-class Classification. There are various algorithms developed in the past like One-class SVM, Support Vector Data Description, OCKELM etc. Tax and Duin developed a MATLAB toolbox for this and it supports various one-class classifiers.
DD Toolbox
One-class SVM
Kernel Ridge Regression based or Kernelized ELM based or LSSVM(where bias=0) based One-class Classification
There is a paper Anomaly Detection Using One-Class Neural Networks
which combines One-Class SVM and Neural Networks.
Here is source code. However, I've had difficulty connecting the source code and the paper.
I have read this line about neural networks :
"Although the perceptron rule finds a successful weight vector when
the training examples are linearly separable, it can fail to converge
if the examples are not linearly separable.
My data distribution is like this :The features are production of rubber ,consumption of rubber , production of synthetic rubber and exchange rate all values are scaled
My question is that the data is not linearly separable so should i apply ANN on it or not? is this a rule that it should be applied on linerly separable data only ? as i am getting good results using it (0.09% MAPE error) . I have also applied SVM regression (fitrsvm function in MATLAB)so I have to ask can SVM be used in forecasting /prediction or it is used only for classification I haven't read anywhere about using SVM to forecast , and the results for SVM are also not good what can be the possible reason?
Neural networks are not perceptrons. Perceptron is on of the oldest ideas, which is at most a single building block of neural networks. Perceptron is designed for binary, linear classification and your problem is neither the binary classification nor linearly separable. You are looking at regression here, where neural networks are a good fit.
can SVM be used in forecasting /prediction or it is used only for classification I haven't read anywhere about using SVM to forecast , and the results for SVM are also not good what can be the possible reason?
SVM has regression "clone" called SVR which can be used for any task NN (as a regressor) can be used. There are of course some typical characteristics of both (like SVR being non parametric estimator etc.). For the task at hand - both approaches (as well as any another regressor, there are dozens of them!) is fine.
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I'm new to the topic of neural networks. I came across the two terms convolutional neural network and recurrent neural network.
I'm wondering if these two terms are referring to the same thing, or, if not, what would be the difference between them?
Difference between CNN and RNN are as follows:
CNN:
CNN takes a fixed size inputs and generates fixed-size outputs.
CNN is a type of feed-forward artificial neural network - are variations of multilayer perceptrons which are designed to use minimal amounts of preprocessing.
CNNs use connectivity pattern between its neurons and is inspired by the organization of the animal visual cortex, whose individual neurons are arranged in such a way that they respond to overlapping regions tiling the visual field.
CNNs are ideal for images and video processing.
RNN:
RNN can handle arbitrary input/output lengths.
RNN unlike feedforward neural networks - can use their internal memory to process arbitrary sequences of inputs.
Recurrent neural networks use time-series information. i.e. what I spoke last will impact what I will speak next.
RNNs are ideal for text and speech analysis.
Convolutional neural networks (CNN) are designed to recognize images. It has convolutions inside, which see the edges of an object recognized on the image. Recurrent neural networks (RNN) are designed to recognize sequences, for example, a speech signal or a text. The recurrent network has cycles inside that implies the presence of short memory in the net. We have applied CNN as well as RNN choosing an appropriate machine learning algorithm to classify EEG signals for BCI: http://rnd.azoft.com/classification-eeg-signals-brain-computer-interface/
These architectures are completely different, so it is rather hard to say "what is the difference", as the only thing in common is the fact, that they are both neural networks.
Convolutional networks are networks with overlapping "reception fields" performing convolution tasks.
Recurrent networks are networks with recurrent connections (going in the opposite direction of the "normal" signal flow) which form cycles in the network's topology.
Apart from others, in CNN we generally use a 2d squared sliding window along an axis and convolute (with original input 2d image) to identify patterns.
In RNN we use previously calculated memory. If you are interested you can see, LSTM (Long Short-Term Memory) which is a special kind of RNN.
Both CNN and RNN have one point in common, as they detect patterns and sequences, that is you can't shuffle your single input data bits.
Convolutional neural networks (CNNs) for computer vision, and recurrent neural networks (RNNs) for natural language processing.
Although this can be applied in other areas, RNNs have the advantage of networks that can have signals travelling in both directions by introducing loops in the network.
Feedback networks are powerful and can get extremely complicated. Computations derived from the previous input are fed back into the network, which gives them a kind of memory. Feedback networks are dynamic: their state is changing continuously until they reach an equilibrium point.
First, we need to know that recursive NN is different from recurrent NN.
By wiki's definition,
A recursive neural network (RNN) is a kind of deep neural network created by applying the same set of weights recursively over a structure
In this sense, CNN is a type of Recursive NN.
On the other hand, recurrent NN is a type of recursive NN based on time difference.
Therefore, in my opinion, CNN and recurrent NN are different but both are derived from recursive NN.
This is the difference between CNN and RNN
Convolutional Neural NEtwork:
In deep learning, a convolutional neural network (CNN, or ConvNet) is a class of deep neural networks, most commonly applied to analyzing visual imagery. ... They have applications in image and video recognition, recommender systems, image classification, medical image analysis, and natural language processing.
Recurrent Neural Networks:
A recurrent neural network (RNN) is a class of artificial neural networks where connections between nodes form a directed graph along a temporal sequence. This allows it to exhibit temporal dynamic behavior. Unlike feedforward neural networks, RNNs can use their internal state (memory) to process sequences of inputs.
It is more helpful to describe the convolution and recurrent layers first.
Convolution layer:
Includes input, one or more filters (as well as subsampling).
The input can be one-dimensional or n-dimensional (n>1), for example, it can be a two-dimensional image. One or more filters are also defined in each layer. Inputs are convolving with each filter. The method of convolution is almost similar to the convolution of filters in image processing. In general, the purpose of this section is to extract the features of each filter from the input. The output of each convolution is called a feature map.
For example, a filter is considered for horizontal edges, and the result of its convolution with the input is the extraction of the horizontal edges of the input image. Usually, in practice and especially in the first layers, a large number of filters (for example, 60 filters in one layer) are defined. Also, after convolution, the subsampling operation is usually performed, for example, their maximum or average of each of the two neighborhood values is selected.
The convolution layer allows important features and patterns to be extracted from the input. And delete input data dependencies (linear and nonlinear).
[The following figure shows an example of the use of convolutional layers and pattern extraction for classification.][1]
[1]: https://i.stack.imgur.com/HS4U0.png [Kalhor, A. (2020). Classification and Regression NNs. Lecture.]
Advantages of convolutional layers:
Able to remove correlations and reduce input dimensions
Network generalization is increasing
Network robustness increases against changes because it extracts key features
Very powerful and widely used in supervised learning
...
Recurrent layers:
In these layers, the output of the current layer or the output of the next layers can also be used as the input of the layer. It also can receive time series as input.
The output without using the recurrent layer is as follows (a simple example):
y = f(W * x)
Where x is input, W is weight and f is the activator function.
But in recurrent networks it can be as follows:
y = f(W * x)
y = f(W * y)
y = f(W * y)
... until convergence
This means that in these networks the generated output can be used as an input and thus have memory networks. Some types of recurrent networks are Discrete Hopfield Net and Recurrent Auto-Associative NET, which are simple networks or complex networks such as LSTM.
An example is shown in the image below.
Advantages of Recurrent Layers:
They have memory capability
They can use time series as input.
They can use the generated output for later use.
Very used in machine translation, voice recognition, image description
...
Networks that use convolutional layers are called convolutional networks (CNN). Similarly, networks that use recurrent layers are called recurrent networks. It is also possible to use both layers in a network according to the desired application!