How do I debug my matlab code?

Hi All,

I need some help debugging my code. It's something minor (I hope), but I can't seem to figure it out.

AbData = rand(756909,16); %%dummy data
tim_trl = 0:3.9634883453625200E-05:30-3.9634883453625200E-05; %%dummy time

t1 = 20; %start time, seconds
t2 = 30; %end time, seconds

ind1 = find(tim_trl>=t1, 1);
ind2 = find(tim_trl>=t2, 1); %10s time frame

time1 = tim_trl(ind1:ind2);

sampRate = 24414; %sampling freq (Hz), samples per sec
muaWindow = 0.001; %1ms window

binWidth = round(muaWindow*sampRate); %24 samples per 1ms


threshold = 0.018; 


for channel = 1:16
    
    data = AbData(ind1:ind2,channel);   
    counterMUA = 1;  % needed for mua indexing
    windowSt = 1;  % set start point of window

    for bin = 1:10000
        
        %set end point of window
        windowEnd = binWidth + windowSt - 1;
        
        % access data in one bin
        bindata = data(windowSt:windowEnd, channel); %debug here
        
        %%calculate mua above threshold
        mua(counterMUA, channel) = sum(bindata >= threshold);
         
        counterMUA = counterMUA+1;
        
        %slides window
        windowSt = windowSt + binWidth;
        
    end
end

This is the line of code that needs debugging:

bindata = data(windowSt:windowEnd, channel); %debug here

I know the index in position 1 exceeds array bounds, but I'm not sure how to overcome it.

Thanks in advance.

Answer 1

[per isakson]

How do I debug my matlab code?

1. Before trying to fix the problem see: Debug a MATLAB Program, then
2. add a breakpoint to line 34, "bindata = data( ..."
3. run the script, execution halts at line 34
4. inspect the values of variables on line 34, data turns out to be empty, why is data empty?
5. look for data in preceeding lines, data is assigned a value at line 24
6. inspect (use the tooltip, hover over variables) the values of the variables on RHS in line 34 (shall be 24), ind2 is empty
7. look for ind2 in preceeding lines, it's assigned in line 9
8. in the command window run

    K>> any(tim_trl>=t2)
    ans =
    logical
        0
    K>> 

No value of tim_trl is larger or equal to the value of t2

That's a copy&paste error (I think). The line should read

    ind2 = find(tim_trl<=t2, 1); %10s time frame

That didn't solve the problem. No, it should read

    ind2 = find(tim_trl<=t2, 1, 'last' ); %10s time frame

And there are more problems.

Index in position 2 exceeds array bounds (must not exceed 1).
Error in cssm (line 34)
        bindata = data(windowSt:windowEnd, channel); %debug here         

At this point data is a column vector and channel has the value 2. Logical mistake, line 24 creates a column vector, channel is accounted for in line 24. Thus

        bindata = data(windowSt:windowEnd); %debug here  
        

Now the script runs without errors. Inspect the result. In the command window run

        imagesc(mua)
        

[NA]

Thank you, this is very helpful.