How do I eliminated the first negative element?

With this variable:

 A = 
      Columns 1 through 4
        [1000x9 double]    [1000x9 double]    [1000x9 double]    [1000x9 double]
      Columns 5 through 8
        [1000x9 double]    [1000x9 double]    [1000x9 double]    [1000x9 double]

My issue is to by-pass (or not consider) the rows that start with a negative number in the first column. I want treat the 8 different arrays as independent ones with regards to ignoring rows that start with a negative number in the first column?. As anyone have an idea?

[the cyclist]

Just to clarify a couple things:

• When you say "bypass", "not consider" or "ignore", do you mean you want to delete those rows, or something else?
• A is a 1x8 cell array, each cell is a matrix of doubles, right?

Answer 1

[the cyclist]

Assuming you want to delete the rows in which the first column is negative, then this should do the trick:

% Fill in some fake data
A = cell(1,8);
for i = 1:8
    A{i} = rand(1000,9) - 0.5;
end

% Create a cell array where the matrices have the leading-negative rows deleted
B = cellfun(@(x) x(x(:,1)>=0,:), A, 'UniformOutput', false)

[Francesco]

Dear cycist you are right. Yes, I want to delete the rows in which the first columns is negative! Why do you do:

    A{i} = rand(1000,9) - 0.5;

Why 0.5=

[the cyclist]

The first part of that code was just to create some fake data that had some rows starting with positive and some negative.

[Francesco]

Ok, thanks! Your line of code run well!