euler_improved_syms.m

来自「数值分析, 同济大学教材<<现代数值数学和计算>>数值分」· M 代码 · 共 11 行

function y = euler_improved_syms(f, y0, h, a, b)
y(1) = y0;
n = (b - a) / h;
x = a : h : b;
syms symx symy;
for i = 1 : n
  y(i+1) = y(i) + h * subs(f, {symx, symy}, {x(i), y(i)});
  y(i+1) = y(i) + h / 2 * (subs(f, {symx, symy}, {x(i), y(i)}) + subs(f, {symx, symy}, {x(i+1), y(i+1)}));
end