A number of issues with the above code --
- Don't use line as a variable, it's a builtin important plotting function,
- size(A) returns a 2-vector, iterating over it is not what you want here, you want only number of columns in A
- While not fatal, you didn't preallocate the output array final which is inefficient altho for such small array won't be noticeable.
Try something more like
nC=size(A,2); % number columns in A
magicNo=9; % make variable; don't bury in code so can change easily
res=nan(nC,1); % output vector preallocation
for c=1:nC % iterate over columns
C=find(A(:,c)>=magicNo); % get vector of locations
if isempty(C), continue, end % skip if none found, leaves output NaN
res(c)=range(C); % save the range of found locations
end
