How to change a matrixvalue dependent on the previous matrixvalue?

Question

Klaas 2017-2-20

0
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https://ww2.mathworks.cn/matlabcentral/answers/325923-how-to-change-a-matrixvalue-dependent-on-the-previous-matrixvalue

回答： Akira Agata 2017-2-20

Hellow

I made this code including for loops but this is very time consuming. My goal is that in the T1 matrix a 1 in placed when the value of matrix T changes from 0 to 1 when looking down in the collum. When the next value of T is again a 1 the T1 matrix must give a 0. So I want to count the number of times the matrix value of T changes from 0 to 1. Has anyone a quicker alternative then this?

for ii=1:4; for jj=1:9 if T(jj+1,ii)>0 && T(jj,ii)<T(jj+1,ii); T1(jj,ii)=1; end end end

Many thanks in advance!

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Klaas 2017-2-20

在 MATLAB Online 中打开

for ii=1:4;
  for jj=1:9
     if T(jj+1,ii)>0 && T(jj,ii)<T(jj+1,ii);
        T1(jj,ii)=1;
     end
  end
end

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Answer 1

Akira Agata 2017-2-20

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/325923-how-to-change-a-matrixvalue-dependent-on-the-previous-matrixvalue#answer_255525

在 MATLAB Online 中打开

I think the following code should be alternative.

idx = [(T(2:end,:) > 0) & (T(1:end-1,:) < T(2:end,:)); logical(zeros(1,size(T,2)))]
T1(idx) = 1;

Let me check whether it works correctly by following.

T = randi([0 1], 10, 4); % Randomly generated 0/1 array
T1 = zeros(size(T));
T2 = zeros(size(T));
 % Original code
 for ii=1:4;
  for jj=1:9
     if T(jj+1,ii)>0 && T(jj,ii)<T(jj+1,ii);
        T1(jj,ii)=1;
     end
  end
 end
 % Proposed code
 idx = [(T(2:end,:) > 0) & (T(1:end-1,:) < T(2:end,:)); logical(zeros(1,size(T,2)))]
 T2(idx) = 1;