Analyzing data using &&

I am trying to analyze my data that meet two conditions. This seems simple but I keep stumbling on this error:

Operands to the || and && operators must be convertible to logical scalar values.

Error in ROI_test2 (line 28)

Here is the code I am using:

%%Load data
data_test = load('test.txt');
[n_x n_y] = size(data_test);
df_data = diff (data_test);
counter = 0;
diff_data=NaN(n_x-1,n_y);
var_data=NaN(n_x-1,n_y);
%% Process raw data to find first derivative and moving variance
for i = 1:n_y
    trace_data = data_test(:,i);
    diff_data(:,i) = diff(trace_data);
    figure (1)
    subplot(3,1,1)
    plot(trace_data)
    subplot(3,1,2)
    plot(diff_data(:,i))
    subplot(3,1,3)
    var_data(:,i) = movvar(diff_data(:,i),5);
    plot(var_data(:,i));
    title(i)
    thresh_pos = max(diff_data(:,i));
    thresh_neg = min(diff_data(:,i));
    stdvar = std (var_data);
    if abs(thresh_neg) >= 0.35*thresh_pos && var_data > 6*stdvar
        %pause
        counter = counter +1;
        particles_identified(:,counter) = i;
    end
end
%% Display the number of positive events
disp(length(particles_identified))

[SL: edited to format the code as code and to smart indent it]

Answer 1

[Steven Lord]

Your variables thresh_neg and thresh_pos are the min or max respectively of a vector of data and so are scalars. This means the result of abs(thresh_neg) >= 0.35*thresh_pos is a logical scalar.

Your variable var_data is a non-vector as soon as i = 2, and so the result of var_data > 6*stdvar is also a matrix. That's why you receive that error.

What do you want to do with your particle identification if statement in that case?

[Mukhtar Ahmed]

Thank you Steven. That helps to understand. I want to know how many of the columns have data that satisfy the two criterion. For the first criterion if is self explanatory. The second condition I need is to add another filter data with peaks that have x times larger than the background standard deviation.