MATLAB: Error using trainNetwork. Unable to read file.

Question

I am trying to implement CNN on signal's Data. I have a database in which I have 10 folders(Each folder has 12 subfolders). Each file has dimensions 12×2000 which is a .mat file. While running CNN on the above data I am facing below attached error. Can someone help me out?

location = 'C:\Users\AKRA\Desktop\New folder (3)';
imds = imageDatastore(location, 'FileExtensions', '.mat', 'IncludeSubfolders',1, ...
                      'LabelSource','foldernames');
                  
  labelCount = countEachLabel(imds)
  img = readimage(imds,1);
size(img)
numTrainFiles = 8;
[imdsTrain,imdsValidation] = splitEachLabel(imds,numTrainFiles,'randomize');
layers = [
    imageInputLayer([12 2000 1])
    
    convolution2dLayer(3,8,'Padding','same')
    batchNormalizationLayer
    reluLayer
    
    maxPooling2dLayer(2,'Stride',2)
    
    convolution2dLayer(3,16,'Padding','same')
    batchNormalizationLayer
    reluLayer
    
    maxPooling2dLayer(2,'Stride',2)
    
    convolution2dLayer(3,32,'Padding','same')
    batchNormalizationLayer
    reluLayer
    
    fullyConnectedLayer(10)
    softmaxLayer
    classificationLayer];
options = trainingOptions('sgdm', ...
    'InitialLearnRate',0.01, ...
    'MaxEpochs',4, ...
    'Shuffle','every-epoch', ...
    'ValidationData',imdsValidation, ...
    'ValidationFrequency',30, ...
    'Verbose',false, ...
    'Plots','training-progress');
net = trainNetwork(imdsTrain,layers,options);
YPred = classify(net,imdsValidation);
YValidation = imdsValidation.Labels;
accuracy = sum(YPred == YValidation)/numel(YValidation)

Answer 1

I think it is expecting more traditional types of image files like .jpg,.png, etc.. I think for .mat you need to specify a specialized ReadFcn. Maybe this?

imds = imageDatastore(location, 'FileExtensions', '.mat', 'IncludeSubfolders',1, ...
                      'LabelSource','foldernames',...
                      'ReadFcn',@(f) getfield(load(f)),___);