matlab利用for循环拟合曲线
时间: 2023-10-02 17:12:51 浏览: 52
以下是一个利用for循环拟合曲线的matlab代码示例:
假设我们要拟合一个二次曲线y = ax^2 + bx + c,其中已知x和y的值:
x = [1, 2, 3, 4, 5];
y = [3, 7, 12, 18, 25];
我们可以使用for循环来拟合曲线,具体步骤如下:
1. 初始化a、b、c的值:
a = 0;
b = 0;
c = 0;
2. 设置迭代次数和学习率:
iterations = 1000;
alpha = 0.01;
3. 开始迭代,更新a、b、c的值:
for i = 1:iterations
h = a * x.^2 + b * x + c;
J = (1 / (2 * length(y))) * sum((h - y).^2);
temp_a = a - alpha * (1 / length(y)) * sum((h - y) .* x.^2);
temp_b = b - alpha * (1 / length(y)) * sum(h - y);
temp_c = c - alpha * (1 / length(y)) * sum(h - y);
a = temp_a;
b = temp_b;
c = temp_c;
end
4. 输出拟合结果:
fprintf('a = %f, b = %f, c = %f', a, b, c);
完整代码如下:
x = [1, 2, 3, 4, 5];
y = [3, 7, 12, 18, 25];
a = 0;
b = 0;
c = 0;
iterations = 1000;
alpha = 0.01;
for i = 1:iterations
h = a * x.^2 + b * x + c;
J = (1 / (2 * length(y))) * sum((h - y).^2);
temp_a = a - alpha * (1 / length(y)) * sum((h - y) .* x.^2);
temp_b = b - alpha * (1 / length(y)) * sum(h - y);
temp_c = c - alpha * (1 / length(y)) * sum(h - y);
a = temp_a;
b = temp_b;
c = temp_c;
end
fprintf('a = %f, b = %f, c = %f', a, b, c);
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