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how set diagonal =1 in matrix tridimensional a(:,:,:)

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aldo
aldo 2023-7-19
编辑： Bruno Luong 2023-7-20
hi,
how can i set=1 the diagonal of the multidimensional matrix
size(COR)
ans =
8 8 188
  8 个评论
显示 6更早的评论
Bruno Luong
Bruno Luong 2023-7-20
编辑：Bruno Luong 2023-7-20
Ran in:
Here is the timings of three methods
COR = rand(8,8,188);
timeit(@() methodfor(COR)) % Aldo
ans = 4.0301e-05
timeit(@() methodlogical(COR)) % Walter
ans = 2.3801e-05
timeit(@() methodindex(COR)) % Bruno
ans = 1.6800e-05
function COR = methodfor(COR)
[r,c,d]=size(COR);
for i=1:d
for x=1:r
COR(x,x,i)=1;
end
end
end
function COR = methodlogical(COR)
M = repmat(logical(eye(size(COR,1),size(COR,2))),1,1,size(COR,3));
COR(M) = 1;
end
function COR = methodindex(COR)
[b,c,d] = size(COR);
COR(1+(b+1)*(0:min(b,c)-1)'+b*c*(0:d-1)) = 1;
end

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回答（3 个）

Geovane Gomes
Geovane Gomes 2023-7-19
Ran in:
Maybe using eye and repmat
COR = repmat(eye(8),1,1,188);
size(COR)
ans = 1×3
8 8 188
Bruno Luong
Bruno Luong 2023-7-20
Ran in:
% Generate dummy test data
a = 0.01*rand(2,3,4)
a =
a(:,:,1) = 0.0058 0.0073 0.0096 0.0027 0.0011 0.0010 a(:,:,2) = 0.0081 0.0020 0.0006 0.0038 0.0068 0.0023 a(:,:,3) = 0.0052 0.0037 0.0065 0.0073 0.0024 0.0026 a(:,:,4) = 0.0057 0.0047 0.0098 0.0098 0.0082 0.0040
[b,c,d] = size(a);
[I,K] = ndgrid(1:min(b,c),1:d);
a(sub2ind([b,c,d],I,I,K)) = 1;
a
a =
a(:,:,1) = 1.0000 0.0073 0.0096 0.0027 1.0000 0.0010 a(:,:,2) = 1.0000 0.0020 0.0006 0.0038 1.0000 0.0023 a(:,:,3) = 1.0000 0.0037 0.0065 0.0073 1.0000 0.0026 a(:,:,4) = 1.0000 0.0047 0.0098 0.0098 1.0000 0.0040
Bruno Luong
Bruno Luong 2023-7-20
Ran in:
% Generate dummy test data
a = 0.01*rand(2,3,4)
a =
a(:,:,1) = 0.0023 0.0073 0.0085 0.0021 0.0024 0.0021 a(:,:,2) = 0.0073 0.0066 0.0072 0.0021 0.0099 0.0025 a(:,:,3) = 0.0035 0.0094 0.0085 0.0008 0.0069 0.0050 a(:,:,4) = 0.0070 0.0079 0.0051 0.0071 0.0029 0.0022
[b,c,d] = size(a);
a(1+(b+1)*(0:min(b,c)-1)'+b*c*(0:d-1)) = 1;
a
a =
a(:,:,1) = 1.0000 0.0073 0.0085 0.0021 1.0000 0.0021 a(:,:,2) = 1.0000 0.0066 0.0072 0.0021 1.0000 0.0025 a(:,:,3) = 1.0000 0.0094 0.0085 0.0008 1.0000 0.0050 a(:,:,4) = 1.0000 0.0079 0.0051 0.0071 1.0000 0.0022

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