% Plot exact y values against cubic spline y values
% and compute absolute error
clear
close all

load hw31.dat
x = hw31(:,1);
y = hw31(:,2);

S = spline(x,y);
xo = linspace(x(1),x(end),51)';
yo = ppval(xo,S);
yexact = hw31fun(xo);
re = (yo-yexact);

figure(2)
   semilogy(xo,abs(re))