18-Nov-2013


1> % Il fenomeno di Runge, si veda Quarteroni-Saleri, pagg. 83, 84.


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)
nodi =

  -5.00000  -3.75000  -2.50000  -1.25000   0.00000   1.25000   2.50000   3.75000   5.00000



8> ynodi = f(nodi);


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


10> length(polint)
ans =  9


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,'k')


19> quit