function y = target3(x) if size(x, 3) ~= 3 error('x must be an Nx3 matrix'); end y =x(:,1).^3+2*x(:,2)-5.*x(:,3); end,错误使用 target3 (第 3 行) x must be an Nx3 matrix,如何改正
时间: 2023-11-09 18:08:29 浏览: 27
这个错误是因为输入的矩阵 x 的第三个维度不是 3。你需要确保 x 是一个 Nx3 的矩阵,其中 N 是任意正整数。如果你想自动将输入的矩阵 x 转换为 Nx3 的矩阵,可以尝试以下修改:
```MATLAB
function y = target3(x)
if numel(size(x)) ~= 2 || size(x, 2) ~= 3
error('x must be an Nx3 matrix');
end
if size(x, 1) == 1 && size(x, 2) > 1
x = x.';
end
y = x(:,1).^3 + 2*x(:,2) - 5.*x(:,3);
end
```
这个修改会检查输入矩阵 x 是否满足要求,并在必要时将其转换为 Nx3 矩阵。
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function y = target3(x) if numel(size(x)) ~= 2 || size(x, 2) ~= 3 error('x must be an Nx3 matrix'); end if size(x, 1) == 1 && size(x, 2) > 1 x = x.'; end y = x(:,1).^3 + 2.*x(:,2) - 5.*x(:,3); end function [samples, acceptance_rate] = mcmc(target3, prop_dist, init_sample, n_samples) samples = zeros(n_samples, 3); samples(1, :) = init_sample; acceptance_rate = 0; for i = 2:n_samples prop_sample = prop_dist.sample(); if size(prop_sample, 2) ~= 3 || size(samples(i-1,:), 2) ~= 3 error('prop_sample and samples must be Nx3 matrices'); end target_ratio = target3(prop_sample)/target3(samples(i-1, :)); prop_ratio = mvnpdf(samples(i-1, :), prop_sample, prop_dist.sigma)/mvnpdf(prop_sample, samples(i-1, :), prop_dist.sigma); alpha = min(1, target_ratio*prop_ratio); if rand() < alpha samples(i, :) = prop_sample; acceptance_rate = acceptance_rate + 1; else samples(i, :) = samples(i-1, :); end prop_dist.update(samples(1:i, :)); end acceptance_rate = acceptance_rate/n_samples; end %% 出错 target3 (第 8 行) y = x(:,1).^3 + 2.*x(:,2) - 5.*x(:,3); 出错 mcmc (第 12 行) target_ratio = target3(prop_sample)/target3(samples(i-1, :)); %% 如何改正
在计算 `target_ratio` 时,需要将 `target3` 函数的输出值转化为标量,而不是一个向量。可以使用 `sum` 函数将向量的元素加和,得到一个标量。修改后的代码如下:
```
function y = target3(x)
if numel(size(x)) ~= 2 || size(x, 2) ~= 3
error('x must be an Nx3 matrix');
end
if size(x, 1) == 1 && size(x, 2) > 1
x = x.';
end
y = sum(x(:,1).^3 + 2.*x(:,2) - 5.*x(:,3)); % 修改此行
end
function [samples, acceptance_rate] = mcmc(target3, prop_dist, init_sample, n_samples)
samples = zeros(n_samples, 3);
samples(1, :) = init_sample;
acceptance_rate = 0;
for i = 2:n_samples
prop_sample = prop_dist.sample();
if size(prop_sample, 2) ~= 3 || size(samples(i-1,:), 2) ~= 3
error('prop_sample and samples must be Nx3 matrices');
end
target_ratio = target3(prop_sample)/target3(samples(i-1, :));
prop_ratio = mvnpdf(samples(i-1, :), prop_sample, prop_dist.sigma)/mvnpdf(prop_sample, samples(i-1, :), prop_dist.sigma);
alpha = min(1, target_ratio*prop_ratio);
if rand() < alpha
samples(i, :) = prop_sample;
acceptance_rate = acceptance_rate + 1;
else
samples(i, :) = samples(i-1, :);
end
prop_dist.update(samples(1:i, :));
end
acceptance_rate = acceptance_rate/n_samples;
end
```
[Ke, Fe] = planeStressStiffness(E,nu, h, x, y,nodeID);matlab子程序
这是一个 MATLAB 子程序,用于计算平面应力状态下的刚度矩阵。输入参数包括杨氏模量 E、泊松比 nu、板厚度 h、节点坐标 x 和 y,以及节点编号 nodeID。输出结果为刚度矩阵 Ke 和应力矩阵 Fe。
具体实现过程可以参考以下代码:
```matlab
function [Ke, Fe] = planeStressStiffness(E,nu, h, x, y,nodeID)
% 定义常数
C1 = E/((1+nu)*(1-2*nu));
C2 = C1*(1-nu);
C3 = 0.5*C1*nu/(1-nu);
% 初始化刚度矩阵和应力矩阵
Ke = zeros(3,3);
Fe = zeros(3,1);
% 计算雅可比矩阵和行列式
J = [x(2)-x(1), x(3)-x(1); y(2)-y(1), y(3)-y(1)];
detJ = det(J);
% 计算面积,板厚度和系数
A = 0.5*detJ;
B = h/6;
C = A*B;
% 计算形函数和形函数导数
N1 = (y(2)-y(3))/detJ;
N2 = (y(3)-y(1))/detJ;
N3 = (y(1)-y(2))/detJ;
Nx1 = (y(2)-y(3))/detJ;
Nx2 = (y(3)-y(1))/detJ;
Nx3 = (y(1)-y(2))/detJ;
Ny1 = -(x(2)-x(3))/detJ;
Ny2 = -(x(3)-x(1))/detJ;
Ny3 = -(x(1)-x(2))/detJ;
% 计算刚度矩阵
Ke(1,1) = C*(Nx1^2 + Ny1^2) + C2*A;
Ke(1,2) = C*(Nx1*Nx2 + Ny1*Ny2) + C2*A;
Ke(1,3) = C*(Nx1*Nx3 + Ny1*Ny3) + C2*A;
Ke(2,2) = C*(Nx2^2 + Ny2^2) + C2*A;
Ke(2,3) = C*(Nx2*Nx3 + Ny2*Ny3) + C2*A;
Ke(3,3) = C*(Nx3^2 + Ny3^2) + C2*A;
Ke(2,1) = Ke(1,2);
Ke(3,1) = Ke(1,3);
Ke(3,2) = Ke(2,3);
% 计算应力矩阵
Fe(1) = -C3*(nu*Nx1 + Ny1);
Fe(2) = -C3*(nu*Nx2 + Ny2);
Fe(3) = -C3*(nu*Nx3 + Ny3);
end
```
请注意,这只是一个参考实现,具体实现方式可能因应用场景而异。