MATLAB: Problem with for loop

for loop

Hallo,
I have a large matrix let's say A 150 * 220000 , including columns that are set entirely to zero .
I want to find '' column wise'' the first element that is larger than 5 and the first element smaller than 200 and store them as two vectors
I creat a for loop, but it breaks when it reaches the first zero column in the matrix. so instead of idx_start 1 * 220000 , I get idx_start 1 * 15000
how can i modify my code so the loop continue over the zero columns?
and would be better if I replaced the zero columns with NaN?
I tried something with isempty but it does not work like I want.
wenn the condition is not met, it is enough to be replaced with NaN
[nx,ny] = size(A) ;
for j = 1:ny  
idx_start(:,j) = find(A(:,j)> 5 ,1,'first') ; 
 if (isempty(A(:,j)))
                continue  
 idx_end(:,j) = find (A(:,j) < 200 , 1, 'first');
  
   end
end

Best Answer

s = size(A,2);
[ii,jj] = find(cumsum(cat(3,A > 5,A < 200)) == 1);
out = accumarray([rem(jj-1,s)+1,ceil(jj/s)],ii,[s,2],[],nan);
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