clf reset
H=axes('unit','normalized','position',[0,0,1,1],'visible','off');
set(gcf,'currentaxes',H);
str='\fontname{楷書}函數exp(-at)與階躍函數u(t)的卷積';
text(0.22,0.96,str,'fontsize',10);
h_fig=get(H,'parent');
set(h_fig,'unit','normalized','position',[0.1,0.2,0.7,0.4]);
h_axes=axes('parent',h_fig,'unit','normalized','position',...
  [0.1,0.15,0.55,0.7],'xlim',[0 15],'ylim',[0 1.8],'fontsize',8);


h_text1=uicontrol(h_fig,'style','text','unit','normalized','position',...
    [0.67,0.72,0.30,0.10],'horizontal','left','string',...
    {'輸入exp(-at)的系數a,a='},'fontsize',12);
h_edit=uicontrol(h_fig,'style','edit','unit','normalized',...
    'position',[0.67,0.62,0.15,0.10],'horizontal','left',...
    'callback' ,[ ...
    'a=str2num(get(gcbo,''string''));' , ...
    'syms T tao;',...
    't=sym(''t'',''positive'');',...
    'ht=exp(-a*t);',...
    'ut=sym(''Heaviside(t)'');',...
    'uh_tao=subs(ut,t,tao)*subs(ht,t,t-tao);',...
    'yt=simple(int(uh_tao,tao,0,t));',...
    'ezplot(t,yt,[0,5])',...
 
    ]); 

h_push1=uicontrol(h_fig,'style','push','unit','normalized',...
    'position',[0.67,0.37,0.12,0.15],'string','grid on',...
    'callback','grid on');
h_push2=uicontrol(h_fig,'style','push','unit','normalized',...
    'position',[0.67,0.15,0.12,0.15],'string','grid off',...
    'callback','grid off');