Values in column bigger than a variable?

Hi all I have a Data.xls file converted into a matrix and I would like to compare the values in the first column of it with two numbers A and B, which change at a click of the user... So I already made everything except for how to make it compare the entire column 1 with the number A or B and give an error message if there is a value bigger than that.

This is a working code but unfortunately it takes the entire Data matrix and scans it , instead of just the first column.

for i=1:length(Data) 
        if Data(i)>=B 
        M=[M Data(i)]; % concatenating
        msgbox(cat(2,{'Error message. Value bigger than:'} , num2str(B)),'Error'
        end
      end
else
    N=[];
      for i=1:length(Data) 
        if Data(i)>=A
        N=[N Data(i)]; % concatenating
        msgbox(cat(2,{'Error message. Value bigger than:'} , num2str(A)),'Error')
        end
      end

p.s. I would ideally like to show the user the ''address'' of the number with the value bigger than A, B.

Thanks

Answer 1

[Guillaume]

Using a loop for this is extremely inefficient. You can directly completely a matrix to a scalar It's simply:

aboveA = find(data > A);
if ~isempty(aboveA)
   msgbox(sprintf('Values at index %d are bigger than %d', aboveA, A), 'Error');
end
%same with B

[TYo]

Thanks for your quick answer.

[Guillaume]

First column or whole matrix does not matter. There is never a need for a loop when comparing a matrix / vector / part of either with a scalar.

For just the first column:

aboveA = find(data(:, 1) > A);