function newunit = autoscale(axishandle, oldunit)
   % will automatically find the correct y-unites with which to plot something
   
   % AUTHOR: Celso Reyes, Geophysical Institute, Univ. of Alaska Fairbanks
   % $Date$
   % $Revision$
   
   if iscell(oldunit), oldunit = oldunit{1}; end;
   ah = axishandle;
   for n=numel(ah):-1:1
      miny(n) = min(get(ah(n),'ydata'));
      maxy(n) = max(get(ah(n),'ydata'));
   end
   ydatamin = min(miny);
   ydatamax = max(maxy);
   knownunits = {'pm','nm','mm','cm','m','km'};
   knownvals = 10.^[-12,-6,-3,-2,0,3];
   biggest=  log10(max(abs([ydatamin, ydatamax])));
   currentUnitIdx = find(strcmpi(oldunit(1:2),knownunits));
   if isempty(currentUnitIdx),
      newunit= oldunit;
      return
   end
   %biggest_in_meters = biggest * knownvals(currentUnitIdx);
   %convertFrom = knownvals(currentUnitIdx);
   newUnitIdx = find(knownvals <= biggest*.1,1,'last');
   canBeExpressedAs= knownunits(find(knownvals <= biggest*.1));
   convertTo = canBeExpressedAs{end};
   if numel(oldunit)>2
      newunit = [convertTo,oldunit(3:end)];
   else
      newunit = convertTo;
   end
   
   set(ah,'ydata',get(ah,'ydata').*(knownvals(currentUnitIdx)./knownvals(newUnitIdx)));
end
