verify which one is the correct one to calculate

i tried both of those instruction to calculate variance of each blob in one image, both leads to different results, i dont know wich one is the correct one can you please help me

for i=1: numofblobs
   croppedImage = frameRGB(bbox(i, 2):bbox(i, 2)+bbox(i, 4)-1, bbox(i, 1):bbox(i, 1)+bbox(i, 3)-1, :);
       blobVariance(i) = var(double(croppedImage(:)));
    end
OR 

for i=1: numofblobs
    blobVariance(i) = var(double(bbox(i,:)))
end

where

bbox = step(blobAnalysis, binaryimage);

Answer 1

[Walter Roberson]

We would need to see the configuration of your blobanalysis to be sure, but the second code appears to be finding the variance in the coordinates of bounding boxes but the first one appears to be looking at the variance in the content of the images inside the bounding boxes

[bay rem]

thank you Here there is the configuration of blobAnalysis

blobAnalysis = vision.BlobAnalysis('BoundingBoxOutputPort', true, ...
    'AreaOutputPort', false, 'CentroidOutputPort', false, ...
    'MinimumBlobArea', 1700,'MaximumCount',2);

i really need help :(

[Walter Roberson]

Your second code would only find the variance in the coordinates, not in the content. You want the first code.