z=peaks;
h=plot(z(:,33));
x=get(h,'XData');
y=get(h,'YData');
imin=find(min(y)==y);
imax=find(max(y)==y);
%a=min(y)
text(x(imin),y(imin),{'Minmum=',num2str(y(min))},...
    'VerticalAlignment','middle',...
    %'HorizontalAlignment','left',...
    %'FontSize',14)