你可以通过迭代行和列，粘贴r2的所需元素来获得空心矩阵。最简单的方法是跟踪你在r2中的位置。我相信如果你需要的话，可以用三角形数字直接计算r2Slice索引。

r2 = randi(10,276,1);

% 1 + inverse triangular number formula
numrows = 1+sqrt(2.*numel(r2)+1/4)-1/2;
mat = zeros(numrows);

firstelement = 1;
lastelement = numrows-1;
for i = 1:numrows-1
    r2Slice = r2(firstelement:lastelement);
    mat(i,i+1:end) = r2Slice';
    mat(i+1:end,i) = r2Slice;
    firstelement = lastelement+1;
    lastelement = lastelement+numrows-1-i;
end

编辑：因为我无法把它从我的脑海中抹去，这里有一个直接计算指数的版本：

r2 = randi(10,276,1);

% triangular nubmer formulas
triang = @(x)x.*(x+1)./2;
inv_triang = @(x)sqrt(2.*x+1/4)-1/2;

numrows = 1+inv_triang(numel(r2));
mat = zeros(numrows);

firstelement = @(i)triang(numrows-1)-triang(numrows-1-i+1)+1;
lastelement = @(i)firstelement(i)+numrows-1-i;

for i = 1:numrows-1
    r2Slice = r2(firstelement(i):lastelement(i));
    mat(i,i+1:end) = r2Slice';
    mat(i+1:end,i) = r2Slice;
end

试试这个：

r2 = randi(10,24);
r2 = (r2+r2')./2; % make matrix symmetric by adding transpose and divide by 2
r2 = r2 - diag(diag(r2)); % subtract diagonal matrix with diagonal from r2