Problem using parfor: Variable cannot be classified

Hi.

I'm using parfor to increase the performance in my program but I having some trouble in the following code:

function  [p] = perc(img,maxr)
aux=double(img); %save image on an auxiliar matrix
r=3:2:maxr; %box sizes
p=zeros(r(1,length(r))^2,size(r,2)); %a column for each box size
parfor k=1:size(r,2)
     ncaixas=(size(img,1)-r(k)+1)*(size(img,2)-r(k)+1);
     lim=(r(k)/2)-0.5;
          for x=lim+1:(size(img,1)-lim)
               for y=lim+1:(size(img,2)-lim)
                    .
                    .
                    .
                    %ordinary instructions
                    .   
                    .
                    .
                    if(condition)
                         ROT=ROT+1;
                    end
                    p(ROT,k)=p(ROT,k)+ROT;
          end
     end
     p(:,k)=p(:,k)./ncaixas;
end
end

MATLAB says to me that I can't use parfor in this case due to the way the variable p is used.

Is there anything I can do to fix this?

Thank you.

BTW, I'm running R2015b

Answer 1

[Walter Roberson]

You cannot assign to p(ROT,k) in a loop. You should assign to a temporary vector and then afterwards assign the temporary to p(:,k)