Question
I have an array of ground truth objects that I want to pass to the "objectDetectorTrainingData" function. However, when I make a call to this function, I receive the following error message: Error using objectDetectorTrainingData>checkGroundTruthLabelDefinitions (line 438) Expected label definitions to have the same label names. Found a mismatch in element 2 of input groundTruth array. I would have expected "objectDetectorTrainingData" to automatically take the union over all label sets, though this does not appear to be the case. Is there any workaround to achieve this workflow?
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Expert Answer
Neeta Dsouza
PhD Expert
Answered Nov 20, 2025
The ability to pass ground truth objects with differing label sets to "objectDetectorTrainingData" is currently not supported. However, a workaround would be to merge all the ground truth objects in the array into a single ground truth object and passing this result to the function call.
To do this, you need to horizontally concatenate all the "LabelData" tables into a single table, vertically concatenate all the "LabelDefinitions" tables into a single table, and use these results to construct a new ground truth object via the "groundTruth" function.
Note: Some additional processing may be necessary to account for labels used by multiple ground truth objects.
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