ex2.m

数值分析, 同济大学教材<<现代数值数学和计算>>数值分析课程所有算法的matlab代码,所有例程均经过测试,私家珍藏

t = [0 5 10 15 20 25 30 35 40 45 50 55]; 
y = [0 1.27 2.16 2.86 3.44 3.87 4.15 4.37 4.51 4.58 4.02 4.64]; 
n = length(t);
A = ones(n, 3);
for i = 1 : n
  A(i, 3) = t(i);
  A(i, 2) = t(i).^2;
  A(i, 1) = t(i).^3;
end
%star
x = A \ y'
x = [x; 0];
s = polyval(x, t);
plot(t, y, '*', t, s, 'b');
hold on;

x1 = polyfit(t, y, 1);
s1 = polyval(x1, t);
x2 = polyfit(t, y, 2);
s2 = polyval(x2, t);
x3 = polyfit(t, y, 3);
s3 = polyval(x3, t);
plot(t, s1, 'g', t, s2, 'y', t, s3, 'r');