using 'find' in matrix

There is a data called "EMG_data" That is a very large dataset. I want to find the location/index that goes over a threshold. This point where the value goes over the threshold value is called 'onset time'.

if true
 indOn=4*ones(3,15); 
  Edata=5*ones(size(EMG_data(:,2:16))); 
  % Edata is the same size as the original or raw data.

    % Range or duration of one trial
    rg1=marker_2:marker_7; 

    for v1=1:15 
        for r1 = 1:length(EMG_data(rg1,v1+1))
            if EMG_data(r1, v1+1) > Threshold(1,v1) 
                Edata(r1,v1)=1; % assign '1' for the values above the threshold
                indOn(1,v1) = find(Edata(rg1,v1)==1,1); %Index for onset time
            else 
                % if the value is not above threshold, then '0' is assigned
                Edata(r1,v1) = 0;
            end
        end
        if indOn(1,v1)==0
            indOn(1,v1)= marker_7-marker_2+1;
        end
    end
  end

I checked my work with more simple code (below). The below code works, so I based the above code on the simpler code. However, it doe snot work.

if true
  a=[1 5 3 4 5; 1 7 8 9 0; 1 2 3 4 6; 1 6 5 4 3];
ind=zeros(1,5);
u=4*ones(4,5);
%Want to analyze each participant separately
for b=1:5
  for r=1:length(a(:,b))
      if a(r,b)<4
          u(r,b)=1;
          ind(1,b) = find(u(:,b)==1,1);
      else
          %If the participant did not do more than 4 push-ups during 4
          %trials, then I want to assign '5'.
          u(r,b)=0;
      end
  end
  if ind(1,b)==0
      ind(1,b)=75; 
  end
end
end

I am getting 'Subscripted assignment dimension mismatch' error for 'indOn(1,v1) = find(Edata(rg1,v1)==1,1);' line.

When I checked, it seems like the first IF statement of the top code is not working properly. If the code finds a value above the threshold, then I want the code to assign '1'. Otherwise, '0' will be assigned. However, '1's or '0's are not being assigned.

I cannot see why this would no work. What could be done to fix this?

[Walter Roberson]

The code has no variable named "v" so we cannot tell.

Answer 1

[Walter Roberson]

In your code a(r,b) is a scalar variable, so a(r,b)>4 is going to be a scalar and so the result of the find() can only be 0 or 1.

What you should be looking at is find(a(:,b)>4,1)

[Image Analyst]

I'm not even sure the find() is needed. Often when people say they want to know where an array exceeds a threshold they can get by just fine with the logical indexes and don't really need to know actual row and column numbers.