我在matlab中为多个变量做梯度下降,并且代码没有得到我用正常eq得到的预期理论值。即: theta = 1.0e + 05 * 3.4041 1.1063 -0.0665 随着正常eq。我已经实施。matlab中的多变量梯度下降
并与GDM我得到的结果是: THETA = 1.0E + 05 * 2.6618 -2.6718 -0.5954 我不明白这是为什么,也许一些人可以帮我,告诉我在代码中的错误在哪里。
代码:
function [theta, J_history] = gradientDescentMulti(X, y, theta, alpha, num_iters)
m = length(y); % number of training examples
J_history = zeros(num_iters, 1);
thetas = size(theta,1);
features = size(X,2)
mu = mean(X);
sigma = std(X);
mu_size = size(mu);
sigma_size = size(sigma);
%for all iterations
for iter = 1:num_iters
tempo = [];
result = [];
theta_temp = [];
%for all the thetas
for t = 1:thetas
%all the examples
for examples = 1:m
tempo(examples) = ((theta' * X(examples, :)') - y(examples)) * X(m,t)
end
result(t) = sum(tempo)
tempo = 0;
end
%theta temp, store the temp
for c = 1:thetas
theta_temp(c) = theta(c) - alpha * (1/m) * result(c)
end
%simultaneous update
for j = 1:thetas
theta(j) = theta_temp(j)
end
% Save the cost J in every iteration
J_history(iter) = computeCostMulti(X, y, theta);
end
theta
end
感谢。
编辑:数据。
X =
1.0000 0.1300 -0.2237
1.0000 -0.5042 -0.2237
1.0000 0.5025 -0.2237
1.0000 -0.7357 -1.5378
1.0000 1.2575 1.0904
1.0000 -0.0197 1.0904
1.0000 -0.5872 -0.2237
1.0000 -0.7219 -0.2237
1.0000 -0.7810 -0.2237
1.0000 -0.6376 -0.2237
1.0000 -0.0764 1.0904
1.0000 -0.0009 -0.2237
1.0000 -0.1393 -0.2237
1.0000 3.1173 2.4045
1.0000 -0.9220 -0.2237
1.0000 0.3766 1.0904
1.0000 -0.8565 -1.5378
1.0000 -0.9622 -0.2237
1.0000 0.7655 1.0904
1.0000 1.2965 1.0904
1.0000 -0.2940 -0.2237
1.0000 -0.1418 -1.5378
1.0000 -0.4992 -0.2237
1.0000 -0.0487 1.0904
1.0000 2.3774 -0.2237
1.0000 -1.1334 -0.2237
1.0000 -0.6829 -0.2237
1.0000 0.6610 -0.2237
1.0000 0.2508 -0.2237
1.0000 0.8007 -0.2237
1.0000 -0.2034 -1.5378
1.0000 -1.2592 -2.8519
1.0000 0.0495 1.0904
1.0000 1.4299 -0.2237
1.0000 -0.2387 1.0904
1.0000 -0.7093 -0.2237
1.0000 -0.9584 -0.2237
1.0000 0.1652 1.0904
1.0000 2.7864 1.0904
1.0000 0.2030 1.0904
1.0000 -0.4237 -1.5378
1.0000 0.2986 -0.2237
1.0000 0.7126 1.0904
1.0000 -1.0075 -0.2237
1.0000 -1.4454 -1.5378
1.0000 -0.1871 1.0904
1.0000 -1.0037 -0.2237
y =
399900
329900
369000
232000
539900
299900
314900
198999
212000
242500
239999
347000
329999
699900
259900
449900
299900
199900
499998
599000
252900
255000
242900
259900
573900
249900
464500
469000
475000
299900
349900
169900
314900
579900
285900
249900
229900
345000
549000
287000
368500
329900
314000
299000
179900
299900
239500
完整的数据集。
请附上您的数据。 – Daniel
哈确定没有pb它是一个大文件。这就是为什么我没有把它。 :) –
然后创建包含并且失败的人工设置。这是寻求基于数据的问题的唯一有效方法。 – lejlot