在 for 循环中构建对角线

Question

尝试在 for 循环中对角地附加到矩阵：

for ii=1:10
     R1 = [1,2;3,4]; Matrix is always 2x2 but different values each iteration 
     cov = blkdiag(R1);
end

显然这行不通，因为我正在重写该值。我想构建一个由 R1 个值组成的矩阵，例如这个

[ R1,0,0,0...,
   0,R1,0,0...]

我可以使用其他技术实现最终目标，只是好奇它是否可以在 for 循环中完成

Answer 1

R1 = [1,2;3,4];                              %// initial R1 matrix
CurrentOut = R1;                             %// initialise output
for ii = 1:10
    R1 = [1,2;3,4];                          %// placeholder for function that generates R1
    [A,B] = size(CurrentOut);                %// get current size
    tmpout(A+2,B+2)=0;                       %// extend current size
    tmpout(1:A,1:B) = CurrentOut;            %// copy current matrix
    tmpout(A+1:end,B+1:end) = R1;            %// add additional element
    CurrentOut=tmpout;                       %// update original
end

如您所说，for 循环不是执行此操作的最佳方法，但确实可以做到。

Answer 2

只要我们循环和增长矩阵，这个怎么样？

for ii = 1:10
   R1 = [1 2; 3 4];   %// placeholder for function that generates R1
                      %// move this line and next before loop if R1 is static
   [m,n] = size(R1);
   cov(end+1:end+m,end+1:end+n) = R1;
end

在 for 循环中构建对角线

Build Diagonal in for loop

matlab

diagonal