So this is what I tried:
set(groot,'DefaultAxesDataAspectRatioMode','auto')
set(groot,'DefaultAxesPlotBoxAspectRatioMode','auto')
and
set(0,'DefaultAxesDataAspectRatioMode','auto')
set(0,'DefaultAxesPlotBoxAspectRatioMode','auto')
But nevertheless when I plot a figure these properties are still on 'manual' as checked in the property Editor; even though the properties are set to 'auto' which I checked with
get(groot,...