What is the correct syntax for using an augmentedImageDatastore as validation data in trainingOptions for the trainNetwork() function?

I have the following image datastore:

myDataset = imageDatastore('C:\MyData',...
    'IncludeSubfolders',true,...
    'FileExtensions','.png',...
    'LabelSource','foldernames');
[imdsTrain, imdsVal, imdsTest] = splitEachLabel(myDataset, 0.6, 0.2, 'randomized');

Which I then prepare to input into some pre-trained networks:

augimdsTrain = augmentedImageDatastore([227 227 3],imdsTrain,...
    'ColorPreprocessing', 'gray2rgb',...
    'DataAugmentation', augmenter);
augimdsVal = augmentedImageDatastore([227 227 3],imdsVal, ...
    'ColorPreprocessing', 'gray2rgb');
augimdsTest = augmentedImageDatastore([227 227 3],imdsTest,...
    'ColorPreprocessing', 'gray2rgb');

What is the correct syntax for using augimdsVal as 'ValidationData'in trainingOptions? Do I just use the augmented datastore as is (as I've seen in some of the documentation):

options = trainingOptions('sgdm','InitialLearnRate', 0.0001, 'ValidationData', augimdsVal);

Or can I add labels like so:

options = trainingOptions('sgdm','InitialLearnRate', 0.0001, 'ValidationData', {augimdsVal imdsVal.Labels});

Or is there a better way?

Answer 1

[Harsha Priya Daggubati]

Hi,

The name-value pair 'ValidationData' can support only the following types as a value:

1. Image Data Store.
2. Data Store.
3. Table.
4. Cell array of X and Y, where X represents data while Y represents corresponding labels.

So, I guess it is invalid to give labels again as a value.

Refer to the following link:

https://www.mathworks.com/help/deeplearning/ref/trainingoptions.html#namevaluepairarguments

Hope this clarifies your concern!

[Dominic Maguire]

Thanks for the update. I was a little confused as some of the documentation examples such as 'Transfer Learning using AlexNet' use an augmentedImageDatastore as the 'ValidationData' and I was wondering how could validation occur without the labels.

[Harsha Priya Daggubati]

As the imagedataStore has labels, there is no need to explicitly specify labels to augmented image datastore, when we use imds as the argument during creation.

[Dominic Maguire]

Great stuff. That's exactly what I wanted to know. Thanks.