Flexible Node size by using biograph in matlab

Suppose DAG is matrix in following

     0     0     0     0     1     0     0
     0     0     0     0     1     0     0
     0     0     0     0     0     1     0
     0     0     0     0     0     1     0
     0     0     0     0     0     0     1
     0     0     0     0     0     0     1
     0     0     0     0     0     0     0

bg.NodeAutoSize='off'

nodeLabels = {'Unwanted Navigational Route' 'Inadequate weather info' 'Human Error1' 'GPS Error' 'AIS Error' 'ECDIS Error' 'Assitant is not required' };

bg = biograph(DAG, nodeLabels, 'arrowsize', 12);

set(bg.Nodes,'Size',[1,1]);

set(bg.Nodes, 'shape', 'ellipse');

set(bg.Nodes,'FontSize', 16);

bgInViewer = view(bg);

Hope you the people understand that I need the size of the ellipse is large. What should I do in this case?