Change sequence of consecutive trues to falses, in logical array

Question

Enrico Gambini 2022-10-13

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https://ww2.mathworks.cn/matlabcentral/answers/1824678-change-sequence-of-consecutive-trues-to-falses-in-logical-array

编辑： Bruno Luong 2022-10-13

Hello guys!

I would like to find a fast procedure to change from true to false the consecutive trues in a logical array excluding only the first and the last true in the sequence.

For instance:

x=[true;false;false;true;true;true;true;true];

Desired output array should be:

output=[true;false;false;true;false;false;false;true];

Hope the question is clear.

Thank you!

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Answer 1

Bruno Luong 2022-10-13

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https://ww2.mathworks.cn/matlabcentral/answers/1824678-change-sequence-of-consecutive-trues-to-falses-in-logical-array#answer_1073453

编辑：Bruno Luong 2022-10-13

x=[true;false;false;true;true;true;true;true;false;true]'
x = 1×10 logical array
   1   0   0   1   1   1   1   1   0   1
x & ~([false,x(1:end-1)]&[x(2:end),false])
ans = 1×10 logical array
   1   0   0   1   0   0   0   1   0   1

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Answer 2

Chunru 2022-10-13

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x=[true;false;false;true;true;true;true;true]'
x = 1×8 logical array
   1   0   0   1   1   1   1   1
output = x;
dx = diff(x(1:end-1))
dx = 1×6
    -1     0     1     0     0     0
output1 = output(2:end-1);
output1(output1 & (dx==0)) = false;
% Desired output array should be:
output(2:end-1) = output1;
output
output = 1×8 logical array
   1   0   0   1   0   0   0   1
% Desired
[true;false;false;true;false;false;false;true]'
ans = 1×8 logical array
   1   0   0   1   0   0   0   1

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Enrico Gambini 2022-10-13

Thank you for the answer!

It does not work if a false is present after the last true of each sequence, for instance, if I had a vector like this:

x=[true;false;false;true;true;true;true;true;false;true]'
x = 1×10 logical array
   1   0   0   1   1   1   1   1   0   1
output = x;
dx = diff(x(1:end-1))
dx = 1×8
    -1     0     1     0     0     0     0    -1
output1 = output(2:end-1);
output1(output1 & (dx==0)) = false;
% Desired output array should be:
output(2:end-1) = output1;
output
output = 1×10 logical array
   1   0   0   1   0   0   0   0   0   1
%Desired should be
[1,0,0,1,0,0,0,1,0,1]
ans = 1×10
     1     0     0     1     0     0     0     1     0     1