How do I combine regions of regionprops?

Hello, I use regionprops to get different regions within an image.   Obj = regionprops(~bw,{'Area','Extrema','Boundingbox','MajorAxisLength','MinorAxisLength','ConvexHull','Centroid'}); According to some assumptions I would like to recombine some Objs of the struct   For example I would like to combine 2 objects where the y-coordinate of the centroid is quite similar. This means, that the some values, Area, Centroid, Bounding Box have to be recalculated. What would be the correct way to do that?