Splitting Ground Thruth Data

I am training a object detector by following along the following tutorial from MathWorks [1]. Instead of detecting from a video I am using a set of images. Images are labeled using ImageLabeller app. My question is how do i split the images in to train/test datasets. `objectDetectorTrainingData` has sampling factor but I believe thats for sampling from video according to docs sampling factor is 1 for images which loads the whole dataset for training. Once the ground truth data is loaded from the mat file generated from ImageLabeller how do i partion it say 80/20?

[1] https://www.mathworks.com/matlabcentral/fileexchange/69180-using-ground-truth-for-object-detection

Answer 1

[Sai Bhargav Avula]

Hi,

You can split the data from the mat file generated using Image Labeler by using the imageDatastore function.

The code structure would look like this

DatasetPath = fullfile(matlabroot,'your path');

imds = imageDatastore(DatasetPath,'IncludeSubfolders',true,'FileExtensions','.mat','LabelSource','foldernames','ReadFcn',@loadmydata);

[imdsTrain,imdsTest] = splitEachLabel(imds,0.8,'randomize');

function data = loadmydata(filename)
    S = load(filename);
    data = S.data;
end

Hope this helps !

[Hamza Yerlikaya]

Hi,

Thanks for the response. I will try this but in the mean time I have come up with the following solution. Just wanted to make sure if I am on the right track. It seems to to the trick.

PD = 0.20;
cv = cvpartition(size(gTruth.LabelData,1),'HoldOut',PD)

trainGroundTruth = ...
    groundTruth(groundTruthDataSource(gTruth.DataSource.Source(cv.training,:)), ... 
                gTruth.LabelDefinitions, ...
                gTruth.LabelData(cv.training,:))

testGroundTruth = ...
    groundTruth(groundTruthDataSource(gTruth.DataSource.Source(cv.test,:)), ... 
                gTruth.LabelDefinitions, ...
                gTruth.LabelData(cv.test,:))

[Sai Bhargav Avula]

Yes, cvpartition is one way. One thing you need to look is the NumTestSets. I think you might have already looked into this. But just attaching the link as reference.

<https://www.mathworks.com/help/stats/cvpartition-class.html>

[Nada Selim]

Thank you for sharing your code. it helps me to split my dataset as well.