In a column how do I find the first cell to equal 0?

I have this code so far:

for i = 7:length(mydata)

   index = find (mydata{i,1}(:,5))== 0

end

However, this returns all the zeros in the whole matrix, I require a cell reference in column 5 as to when the first 0 occurs.

[Azzi Abdelmalek]

This is not clear

[Franchesca]

I have a matrix and in column 5 I want to find the peak value in the first phase until the numbers change to 0.

So I was trying to find the cell reference of when the first 0 in the column occurs so I can find the peak value from cell 1 to the reference I found.

[Franchesca]

%% Calculate peak power

 [row col] = ((mydata{i,1}(:,5))== 0,'first'); % finding the cell which is first 0 in column

 pp(i,1) = nanmin (mydata {i,1}(:,5)); % finding peak power

pp is finding the peak power in the whole of column 5 however I want to find the first zero then find peak power up to this point

[Christopher Pedersen]

Finding the first zero: you can use additional inputs to "find", to only return the first value found:

loc = find(x==0,1,'first') returns the 1 first times x==0

or loc = find(x==0); loc = loc(1); returns all the occurences of zero, then extracts the first.

Extracting values up to the first zero: y = x(1:loc);

Answer 1

[per isakson]

Run this

    ixc = 3; % third column
    sample_array = num2cell( magic(4)-3 );
    is = cell2mat( sample_array( :, ixc ) ) == 0;

    >> sample_array
    sample_array = 
        [13]    [-1]    [ 0]    [10]
        [ 2]    [ 8]    [ 7]    [ 5]
        [ 6]    [ 4]    [ 3]    [ 9]
        [ 1]    [11]    [12]    [-2]

    >> is
    is =
         1
         0
         0
         0