exm020304.m

来自「matlab电子书籍」· M 代码 · 共 29 行

clear
syms x 
syms d positive
f_p=sin(x);											%
df_p=limit((subs(f_p,x,x+d)-f_p)/d,d,0)             %	<4>
df_p0=limit((subs(f_p,x,d)-subs(f_p,x,0))/d,d,0)	%	<5>  
  


f_n=sin(-x);											
df_n=limit((f_n-subs(f_n,x,x-d))/d,d,0)             % 	<7>
df_n0=limit((subs(f_n,x,0)-subs(f_n,x,-d))/d,d,0)		%<8>  
  

f=sin(abs(x));
dfdx=diff(f,x)												%	<10>  
  


xn=-3/2*pi:pi/50:0;xp=0:pi/50:3/2*pi;xnp=[xn,xp(2:end)];
hold on
plot(xnp,subs(f,x,xnp),'k','LineWidth',2.5)					%	<13>
plot(xn,subs(df_n,x,xn),'--r','LineWidth',2.5)	
plot(xp,subs(df_p,x,xp),':r','LineWidth',2.5)
legend(char(f),char(df_n),char(df_p),'Location','NorthEast')%	<16>
grid on
xlabel('x')
hold off