Error: Attempted to access E(-251); index must be a positive integer or logical

Hi,

I have a function that gives this error. I did not write this code nor do I have anything more then a novice understanding of MATLAB code. Unfortunately, I do not know anyone with the expertise to help me troubleshoot. I've tried messing with abs on the equation in question that gives the error but then the error reads A(-251) and if I abs both of them I get 0. Any help would be greatly appreciated. Thanks!

 function E = findevents(motion,fps,win)

 frames = length(motion);

 L = ceil(fps*win); % 10 second window

 d = 1; % Displace by 1 frame

 E = (10*ones(frames,1));

 A = (10*ones(frames,1));

 for i=floor(L/2):d:frames-(floor(L/2)-d)

     snippet = (motion(i-floor(L/2)+1:i+floor(L/2)-d));

     deviation = (snippet-mean(snippet)).^2;

 E(i) = sqrt(mean(deviation));

 A(i) = mean(snippet);

 end

 % E(A>=.5) = .5;

Error in findevents (line 11) E(i) = (sqrt(mean(deviation)));

Answer 1

[Thorsten]

In Matlab the indices have to be integer numbers > zero. So if you use

   E(i) = sqrt(mean(deviation));
   A(i) = mean(snippet);

you have to ensure that i is always > 0 and integer.

You could probably rewrite the code as follows:

 ind = floor(L/2):d:frames-(floor(L/2)-d);
 for i=1:numel(ind)
   ii = ind(i);
   snippet = (motion(ii-floor(L/2)+1:ii+floor(L/2)-d));
   deviation = (snippet-mean(snippet)).^2;
   E(i) = sqrt(mean(deviation));
   A(i) = mean(snippet);
 end

[Arnold G]

Thank you for the quick reply. I tried your suggestion and it seems that while the indices are now integers >0 my matrix dimensions no longer agree. I'll post the code here before submitting a new question.

Error using  & 
Matrix dimensions must agree.

Error in OpenField_L (line 186)
Sitting_in_corner = evnts<thr & (Location==1 | Location2==1);

The code:

 %%Sitting in a corner - use tail coordinates for this
 Location2 = single(zeros(frames,1));
 for i=start_idx:frames
     if(floor(Tail(i,2))~=0 && floor(Tail(i,1))~=0)
         if(outer_BW_L(floor(Tail(i,2)),floor(Tail(i,1))))
             Location2(i) = 2;
         elseif(inner_BW_L(floor(Tail(i,2)),floor(Tail(i,1))))
             Location2(i) = 3;
         elseif(center_BW_L(floor(Tail(i,2)),floor(Tail(i,1))))
             Location2(i) = 4;
         else
             Location2(i) = 1;
         end
     end
 end
 Sitting_in_corner = evnts<thr & (Location==1 | Location2==1);
 for i=1:length(idx)-1
     TimeSitting_in_corner(1,i) = nnz(Sitting_in_corner(idx(i):idx(i+1)))/fps;
 end
Motion = Motion./px_per_inch_L;

[Walter Roberson]

You don't show us how you created Location so we do not know that it is the same size as Location2. We also have no information about the size of evnts or of thr

[Image Analyst]

Put in these lines before that line of code and tell us what it says

whos evnts
whos thr 
whos Location
whos Location2

[Arnold G]

Thanks for your assistance. As advised, I reran the file. The output was as follows:

 Name        Size        Bytes    Class     Attributes
 evnts       7398x1       59184   double              
 thr         1x1          8       double              
 Location    6894x1       27576   single              
 Location2   6894x1       27576   single

Additionally, I have shared the file in question. Also, if it would better to repost or post elsewhere please let me know. Thanks!

[Walter Roberson]

Your Location and Location2 are the same size so it makes sense to test them with == to get back an array of the same size. But your evnts is a completely different size, about 504 entries larger. For any given Location(J), which evnts should be correspond?