MATLAB: How to find the elements in a matrix that follow a certain pattern

findmatrixmatrix manipulation

Dear All,
I have been working on writing a code to get what I want and have not been luck yet. I hope you can help me to do so so that I can move on with my research. Any help will be appreciated.
I do have a column that has the following format in general:
[0;
 0; % a number of zeros
 .
 .
 5 %please note that the non-zero elements are essentially the row numbers i.e. the fifth element is 5 and so on. 
 6
 7
 8
 0 % again a set of zeros
 0 
 0
 12
 13
 0
 0]
what I want is to write a code that gives me the first and last element of each non-zero interval. for the example above my desired out put would be a matrix of 2*2 as
[5  8
 12  13] % the first and second columns would be including the first and last non zero elements of each interval, respectively.
Thank you so much for your helps. I have been kind of stuck!

Best Answer

This seems to work in the data you presented:
v = [0;
     0;
     0
     5 
     6
     7
     8
     0 
     0 
     0
     12
     13
     0
     0];
nzi = diff([0; v]);
nzigt0 = find(nzi > 1);
nzilt0 = find(nzi < 0);
Output = [v(nzigt0)  v(nzilt0-1)]
Output =
       5     8
      12    13
Related Question