How to index a matrix to make it from a vector, taking some elements from the vector and put them in a new row?

Question

Karla 2022-11-28

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https://ww2.mathworks.cn/matlabcentral/answers/1866028-how-to-index-a-matrix-to-make-it-from-a-vector-taking-some-elements-from-the-vector-and-put-them-in

回答： Stephen23 2022-11-29

I need to construct a matrix taking three elements from a 14-elements vector v(1:3) and write them in a row, then take the next three elements v(2:4) in the next row, and so on. Such that that I need to have something as in the image:

I have this piece of code but the indexing is no correct:

pilots4356 = Rxc1(43:56); %vector
matrix4356 = zeros(12,14); %matrix size
pospilot = 1; %index
for f = 1:12 %rows
    for c = 1:14 %columns
        for pospilot = pospilot:pospilot+2
            matrix4356(:,c) = pilots4356(pospilot);
        end
        pospilot = pospilot+1;
    end
end
matrix4356

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Answer 1

Voss 2022-11-28

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https://ww2.mathworks.cn/matlabcentral/answers/1866028-how-to-index-a-matrix-to-make-it-from-a-vector-taking-some-elements-from-the-vector-and-put-them-in#answer_1114723

在 MATLAB Online 中打开

Here's one way to do it:

pilots4356 = 43:56; %vector
N = numel(pilots4356)-2;
matrix4356 = zeros(N,N+2); %matrix size
% place the vector along the diagonals of the matrix:
matrix4356(1:N+1:N^2) = pilots4356(1:end-2);
matrix4356(N+1:N+1:N^2+N) = pilots4356(2:end-1);
matrix4356(2*N+1:N+1:N^2+2*N) = pilots4356(3:end);
disp(matrix4356);
    43    44    45     0     0     0     0     0     0     0     0     0     0     0
     0    44    45    46     0     0     0     0     0     0     0     0     0     0
     0     0    45    46    47     0     0     0     0     0     0     0     0     0
     0     0     0    46    47    48     0     0     0     0     0     0     0     0
     0     0     0     0    47    48    49     0     0     0     0     0     0     0
     0     0     0     0     0    48    49    50     0     0     0     0     0     0
     0     0     0     0     0     0    49    50    51     0     0     0     0     0
     0     0     0     0     0     0     0    50    51    52     0     0     0     0
     0     0     0     0     0     0     0     0    51    52    53     0     0     0
     0     0     0     0     0     0     0     0     0    52    53    54     0     0
     0     0     0     0     0     0     0     0     0     0    53    54    55     0
     0     0     0     0     0     0     0     0     0     0     0    54    55    56

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Answer 2

Stephen23 2022-11-29

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1866028-how-to-index-a-matrix-to-make-it-from-a-vector-taking-some-elements-from-the-vector-and-put-them-in#answer_1114888

在 MATLAB Online 中打开

A general approach:

V = 43:56;
N = 3;
C = numel(V);
M = V .* tril(triu(ones(C-N+1,C)),N-1);
disp(M)
  44    45     0     0     0     0     0     0     0     0     0     0     0
  44    45    46     0     0     0     0     0     0     0     0     0     0
   0    45    46    47     0     0     0     0     0     0     0     0     0
   0     0    46    47    48     0     0     0     0     0     0     0     0
   0     0     0    47    48    49     0     0     0     0     0     0     0
   0     0     0     0    48    49    50     0     0     0     0     0     0
   0     0     0     0     0    49    50    51     0     0     0     0     0
   0     0     0     0     0     0    50    51    52     0     0     0     0
   0     0     0     0     0     0     0    51    52    53     0     0     0
   0     0     0     0     0     0     0     0    52    53    54     0     0
   0     0     0     0     0     0     0     0     0    53    54    55     0
   0     0     0     0     0     0     0     0     0     0    54    55    56