The CNN model only predicts a single class out of three?
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Hello,
I am working on training a CNN model for pavement distress identification using image classification. I have three categories for defects (Alligator Cracks, Potholes and Rutting). When I run my model it only predicts a single class out of three rendering my model accuracy to 33.33%. I tried changing the training parameters/ options but the result is same. I was hoping if someone can help me figure out why. The code I am using is given below. Thanks in advance.
_______________________________________________________________________________________________________________________________________
rootFolder = fullfile ('CNN Input');
categories = {'Alligator Cracks','Potholes','Rutting'};
imds = imageDatastore (fullfile (rootFolder,categories), 'LabelSource', 'Foldernames');
tbl = countEachLabel (imds);
minSetCount = min(tbl{:,2});
countEachLabel(imds);
AlligatorCracks = find(imds.Labels == 'Alligator Cracks',1);
Potholes = find(imds.Labels == 'Potholes',1);
Rutting = find(imds.Labels == 'Rutting',1);
net = alexnet ();
rng ('default');
net.Layers(1);
net.Layers(end);
numel(net.Layers(end).ClassNames);
[trainingSet, testSet, validationSet] = splitEachLabel(imds,0.75,0.15,'randomize');
imageSize = net.Layers(1).InputSize;
augmentedTrainingSet = augmentedImageDatastore(imageSize,trainingSet,'ColorPreprocessing','gray2rgb');
augmentedTestSet = augmentedImageDatastore(imageSize,testSet,'ColorPreprocessing','gray2rgb');
augmentedValidationSet = augmentedImageDatastore(imageSize,validationSet,'ColorPreprocessing','gray2rgb');
w1 = net.Layers(2).Weights;
w1 = mat2gray(w1);
featurelayer = 'drop7';
trainingFeatures = activations(net, augmentedTrainingSet, featurelayer,'MiniBatchSize', 32,'OutputAs', 'columns');
options = trainingOptions('sgdm', ...
'LearnRateSchedule','piecewise',...
'LearnRateDropFactor',0.2,...
'learnRateDropPeriod',1,...
'MaxEpochs',8,...
'MiniBatchSize',16,...
'Plots','training-progress',...
'Shuffle','once');
numClasses = 3;
layersTransfer = net.Layers(1:end-3);
layers = [
layersTransfer
fullyConnectedLayer(numClasses,'WeightLearnRateFactor',20,'BiasLearnRateFactor',20)
softmaxLayer
classificationLayer];
trainedNet = trainNetwork(augmentedTrainingSet,layers,options);
trainingLabels = trainingSet.Labels;
classifier = fitcecoc(trainingFeatures, trainingLabels, 'Learner', 'Linear', 'Coding', 'onevsall','observationsIn','columns');
testFeatures = activations(trainedNet,augmentedTestSet, featurelayer,'MiniBatchSize', 32,'OutputAs', 'columns');
validationFeatures = activations(trainedNet,augmentedValidationSet, featurelayer,'MiniBatchSize', 32,'OutputAs', 'columns');
predictLabels = predict(classifier,testFeatures,'ObservationsIn','columns');
predictLabelss = predict(classifier,validationFeatures,'ObservationsIn','columns');
testLables = testSet.Labels;
validationLables = validationSet.Labels;
confMat = confusionmat(testLables, predictLabels);
confMatt = confusionmat(validationLables, predictLabelss);
confMat = bsxfun(@rdivide, confMat, sum(confMat,2));
confMatt = bsxfun(@rdivide, confMatt, sum(confMatt,2));
mean(diag(confMat));
mean(diag(confMatt));
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Shishir Singhal
2020년 5월 22일
Hi, You facing this problem may be because of class imbalance.
Just check the number of datapoints you have in each class.
To handle the class imbalance, you can use data augmentation techniques.
For data augmentation in MATLAB, you can refer to this link: https://www.mathworks.com/help/deeplearning/ref/imagedataaugmenter.html
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Shishir Singhal
2020년 5월 27일
편집: Shishir Singhal
2020년 5월 27일
Yes, do data augmentation multiple times.
You can refer to these links to know more about data augmentation techniques:
In your case, it also might happened an unusual split.
For example, it may happen that our training set consist more examples for a particular class. Please check the distribution of each class in train, test and validation set.
Moreover, first apply data augmentation technique in your data. And then do stratified split. Because, if there is an unsual split, and you are applying data augmentation on top of it, then you have almost similiar kind of images in your training set which makes your traning model bias towards a particular class.
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