n=13;
f=inline('1./(1+x.^2)');
t=linspace(-5,5,1000); % NODI TEST.
x=linspace(-5,5,n);     % NODI SUDDIV.
y=feval(f,x);                     % (x,y) COPPIE INTP.
st=interp1(x,y,t,'linear'); 
ft=feval(f,t);
err=norm(ft-st,inf);
fprintf('\n \t err: %2.2e \n',err);