examp3_49.m

matlab的大量实例代码

x=0:.12:1;
y=(x.^2-3*x+5).*exp(-5*x).*sin(x); plot(x,y,x,y,'o')

x1=0:.02:1; y0=(x1.^2-3*x1+5).*exp(-5*x1).*sin(x1);
y1=interp1(x,y,x1); y2=interp1(x,y,x1,'cubic');
y3=interp1(x,y,x1,'spline');
plot(x1,[y1',y2',y3'],':',x,y,'o',x1,y0)
[max(abs(y0(1:49)-y2(1:49))),max(abs(y0-y3))]

p1=polyfit(x,y,3),p2=polyfit(x,y,4),p3=polyfit(x,y,5)

y1=polyval(p1,x1); y2=polyval(p2,x1); y3=polyval(p3,x1);
x0=(x1.^2-3*x1+5).*exp(-5*x1).*sin(x1);
plot(x1,y0,x1,y1,'--',x1,y2,':',x1,y3,'-.')