1> f=inline('1./(1+x.^2)')
f =

f(x) = 1./(1+x.^2)



2> x=linspace(-5,5);


3> y=f(x);


4> plot(x,y)


5> hold on


6> n=9;


7> nodi=linspace(-5,5,n);


8> nodi
nodi =

 Columns 1 through 7:

  -5.00000  -3.75000  -2.50000  -1.25000   0.00000   1.25000   2.50000

 Columns 8 and 9:

   3.75000   5.00000



9> ynodi=f(nodi);


10> polint=polyfit(nodi,ynodi,n-1);


11> ypol=polyval(polint,x);


12> plot(x,ypol,'r')


13> n=13;


14> nodi=linspace(-5,5,n);


15> ynodi=f(nodi);


16> polint=polyfit(nodi,ynodi,n-1);


17> ypol=polyval(polint,x);


18> plot(x,ypol,'g')


19> n=21;


20> nodi=linspace(-5,5,n);


21> ynodi=f(nodi);


22> polint=polyfit(nodi,ynodi,n-1);


23> ypol=polyval(polint,x);


24> plot(x,ypol,'k')


25> hold off


26> xc=-5*cos(pi/8*[0:8]);


27> yc=f(xc); pc=polyfit(xc,yc,n); ypc=polyval(pc,x);


28> yc=f(xc); pc=polyfit(xc,yc,8); ypc=polyval(pc,x);


29> plot(x,ypc,'c',xc,yc,'k+');


30> hold on


31> plot(x,y)


32> n=9;


33> nodi=linspace(-5,5,n);


34> ynodi=f(nodi);


35> polint=polyfit(nodi,ynodi,n-1);


36> ypol=polyval(polint,x);


37> plot(x,ypol,'r')


38> quit