what should be correct format of feature vectors matrix for feeding into neural networks?

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kunwar_ · Jul 22, 2021 · 2K views
Question
I am using MatlabR2012b version. m working on speech emotion classification, i have used MFCC for feature extraction and NNtoolbox for classification, but i am getting very high error rates (training error 23%, validation error 60%, testing error 80%). i tried various combinations of input matrix and target matrix but none helped me. a portion of my code for generating feature vector matrix is here:   mfcc=zeros(6000*13,size(filesToRead,1));   for j=1:size(filesToRead,1) % Read speech samples, sampling rate and precision from file [ speech, fs, nbits ] = wavread( filesToRead{j} ); % Feature extraction (feature vectors as columns) [ MFCCs, FBEs, frames ] = mfcc( speech, fs, Tw, Ts, alpha, hamming, R, M, C, L ); for i=1:13 mfcc((i-1)*size(MFCCs,2)+1:i*size(MFCCs,2),j) = MFCCs(i,:); end clearvars MFCCs end *I have a total of 160 speech samples and eight different classes (20samples each). I have extracted MFCCs and it gives me a 13x5000 matrix for one sample. I want to feed these features for all 160 samples into NN and then classify into 8 classes. tell me stepwise: # (1). in which format to store the feature vector matrix # (2). how to arrange the extracted feature vectors (in rows or columns?) # (3) Whether i need to create one single matrix for the features of all 160 samples? # (4) How do i feed this matrix to NN and how many input neurons should i have? # (5). which divide parameter should be used for dividng my data set into training, validation and testing sets. (i used dividerand and divided as 70-15-15 and also tried 60-20-20 and 70-20-10) # (6) what should be my hidden layer function. (sigmoid, linear etc..) # (7) What should be my target matrix?*
Expert Answer
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Neeta Dsouza PhD Expert
Answered Aug 25, 2026

In MATLAB, the correct format of feature vectors for feeding into neural networks is typically a matrix where each column represents a feature vector and each row represents a different observation (sample). Here’s a general guideline:

1. Matrix Dimensions:
   - For a classification or regression problem, your feature matrix should be of size `N x M`, where `N` is the number of features and `M` is the number of samples.
   - Ensure that each column corresponds to a single observation and each row corresponds to a different feature.

2. Example:
   
   % Example feature matrix with 5 features and 100 samples
   X = rand(5, 100);
   % Example target matrix for 3-class classification with 100 samples
   T = randi([0, 1], 3, 100);  % One-hot encoded targets
   

3. Feed into Neural Network:
   Use the appropriate functions to train the network with your feature matrix. For example, with a pattern recognition network:

   
   % Create a pattern recognition network with 10 hidden neurons
   net = patternnet(10);
   % Train the network
   net = train(net, X, T);
   

4. Additional Preprocessing:
   Ensure your data is preprocessed appropriately (e.g., normalized or standardized) to improve training performance.

By following these guidelines, you can properly format your feature vectors for neural networks in MATLAB. 

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