Whenever I run this function, all is good if A(i)==N. However when it is not found, the function seems to run super slowly that i never end up getting the output of 0. Do I need to preallocate somewhere? If so, what would it be?

"Write a function, Finder, that receives an array of numbers A and a number N and returns the position of N within the array A or the value zero if N is not present within A."

function pos=Finder(A,N)
found=false;

while ~found
    for i=1:length(A);
        if A(i)==N;
            found=true;
            break
        end
    end
end

if found
    pos=i;
else
    pos=0;
end
end

Answer 1

[Walter Roberson]

You should use either a while loop or a for loop, but not both.

[José-Luis]

On top of what Walter said, in your code, if it never gets found, your condition never gets set to true and you never break out of the while loop.

[John D'Errico]

The real question is, why not just use ismember?