Finding zeroes of data for multiple trials

I have found that the answer to another question on MATLAB Answers (found here: Previous Question) works for finding the zeroes of one of my data trials (see code below).

x = QF02num(:,1);
y = QF02num (:,2);

%%Code is from Star Strider in Previous Question (see link above)

zci = @(v) find(v(:).*circshift(v(:), [-1 0]) <= 0);                    % Returns Approximate Zero-Crossing Indices Of Argument Vector

dy = zci(y);                                                            % Indices of Approximate Zero-Crossings
for k1 = 1:size(dy,1)-1
    b = [[1;1] [x(dy(k1)); x(dy(k1)+1)]]\[y(dy(k1)); y(dy(k1)+1)];      % Linear Fit Near Zero-Crossings
    x0(k1) = -b(1)/b(2);                                                % Interpolate :Exact, Zero Crossing
    mb(:,k1) = b;                                                       % Store Parameter Estimates (Optional)
end

However, my data consists of multiple trials. I have a matrix called QF02num(91X81) that has 81 trials of data for which I am wanting to find the zeroes. The length of these trials (or the number of rows) and the number of times the data will cross the x axis both vary from trial to trial.

I have tried adding a for loop to iteratively go through each column or trial but I'm not sure how to store the zeroes (x0) for all the trials into one matrix. How do I make it so x0 stores the values of each iteration or column (i)?

for i=size(QF02num,2);
x = QF02num(:,1);
y = QF02num (:,i);

%%Code is from Star Strider in Previous Question (see link above)

zci = @(v) find(v(:).*circshift(v(:), [-1 0]) <= 0);                    % Returns Approximate Zero-Crossing Indices Of Argument Vector

dy = zci(y);                                                            % Indices of Approximate Zero-Crossings
for k1 = 1:size(dy,1)-1
    b = [[1;1] [x(dy(k1)); x(dy(k1)+1)]]\[y(dy(k1)); y(dy(k1)+1)];      % Linear Fit Near Zero-Crossings
    x0(k1) = -b(1)/b(2);                                                % Interpolate :Exact, Zero Crossing
    mb(:,k1) = b;                                                       % Store Parameter Estimates (Optional)
end

end

I have included a plot of one of the trials for visualization:

Answer 1

[Image Analyst]

Assuming mb is your signal that you plotted, you can count the number of regions where the signal is above zero with this:

[, count] = bwlabel(mb > 0);