MATLAB: How to find position of something

homeworknanposition;

Hi, I am having a problem with part of my homework. I have a column with numbers and NaN-s. If I have 5 or more NaN-s in a row I need to know place/position where NaN start (j) and end (i) ( in all column). For example 7 6 5 NaN NaN NaN NaN NaN NaN 9 7
j=4 i=9 Thanks you very much 🙂

Best Answer

You can use the 'find' and 'diff' functions as well as 'isnan' to accomplish that. Let A be your column vector of elements with possible NaNs among them.
 m = 5; % The minimum length of consecutive NaNs to record
 f = find(diff([false;isnan(A);false]));
 B = [f(1:2:end-1),f(2:2:end)-1]; % Get all start and end indices for NaN consecutive sequences
 B = B(B(:,2)-B(:,1)+1>=m,:); % Eliminate all with fewer than m NaNs
The first column of array B contains the start indices and the second column the end indices for consecutive sequences of at least five NaNs.
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