improve performance of this code

suppose to have a matrix called A

3 0 3 3
0 0 4 0

and have this function

while(1)
  if all(A(:,i) == 0)
    i = i + 1;
  else
    i = i + 1
    break;
  end
end

How can I improve the performance of this code?

[Azzi Abdelmalek]

What do you want to find?

[Salvatore Mazzarino]

I want to find the index that rappresents the column where there are at least one element

Answer 1

[Jan]

I cannot imagine that you can feel the speedup for such a tiny problem.

k = 1;             % Avoid using "i" as variable
while(1)
  if any(A(:, k))  % This saves the creation of the temp logical vector
    k = k + 1;
    break;
  else
    k = k + 1
  end
end

Note that you function will crash, when A contains zeros only. More secure:

index = NaN;
for k = 1:size(A, 2)
  if any(A:, k)
    index = k;
    break;
  end
end

Now index is a NaN, if no column matches the condition.

Shorter:

k = find(any(A, 1), 1);

For large A this must be slower, if a matching column appears early.

[Salvatore Mazzarino]

i variable is important in my code. it's incremented during the execution of my code. it cannot be fixed

Answer 2

[Matt J]

 i = find(any(A,1) ,1)

Answer 3

[Azzi Abdelmalek]

out= min(find(any(A)))

%or

ii= 1;            
while(1)
if any(A(:,ii)) 
break;
else
  ii= ii+1
end
end