Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_estimate_units”.

  FT_ESTIMATE_UNITS tries to determine the units of a geometrical object by
  looking at its size and by relating this to the approximate size of the
  human head according to the following table:
    from  0.050 to   0.500 -> meter
    from  0.500 to   5.000 -> decimeter
    from  5.000 to  50.000 -> centimeter
    from 50.000 to 500.000 -> millimeter
 
  Use as
    unit = ft_estimate_units(size)
 
  This function will return one of the following strings
    'm'
    'dm'
    'cm'
    'mm'
 
  See also FT_CONVERT_UNITS