How to change index value of logical array.

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Hello everyone i hope you are doing well. I have the following logical array in which some values are 1 for example
the value for index 13 to 17 are 1.
  • first i want to find where 1 values exist.
  • then find minimum and maximum value where 1 exist.
  • Then I want to change minimum and maximum index for example if 1 exist in 13 index the 50 were added to it and new index is 63 and new index for 17 is 67.
now the minimum value is 63 and maximum value is 67 where 1 value exist.
How can i do it in MATLAB

Accepted Answer

Walter Roberson
Walter Roberson on 4 Aug 2022
locs = find(Mask);
first = locs(1);
last = locs(end);
With regards to changing the index: what do you want to do if there are 1s within the last 50 entries? Do you want to put 50 0's at the beginning, making the whole thing 50 longer? Do you want to shift by 50 but the array should stay the same length provided that no 1s were moved outside of the original length? But if some 1s got moved outside the original length should the array become longer but ending at the last 1?
  4 Comments
Walter Roberson
Walter Roberson on 4 Aug 2022
idx = find(mask);
row1 = min(idx);
row2 = max(idx);
shifted_mask = circshift(mask, 50);

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