Hi Raghad,
I understand that you are trying to calculate the log miss rate using evaluateDetectionMissRate(). But your second input argument is wrong.
If you are using image data store. You can go for this approach instead
blds = boxLabelDatastore(testData(:,2:end));
[am, fppi, missRate] = evaluateDetectionMissRate(detectionResults,blds);
You can refer to Evaluate miss rate metric for object detection - MATLAB evaluateDetectionMissRate (mathworks.com) for more information about evaluateDetectionMissRate() function and to Datastore for bounding box label data - MATLAB (mathworks.com) for information about boxLabelDatastore.