Using for loop to extract data from a matrix

I am trying to etract certain data from a matrix into a single row vector with the length of the vector depending on the number of elements in the atrix.

So for example I extracted successfully the element numbers that represents one building component with the following code:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Assign Elements to part Cavity
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

groupc=strfind(aName,'Cavity');

tf= cellfun('isempty',groupc); %tf gives 1, if cell contains []

for i=1:length(tf) %converts [] to 0
       
    if tf(i)==1
        
        groupc(i)={0};
    end
end

groupc=cell2mat(groupc);

combic= [aElements,groupc]; %aElements is defined as a cell array containing all existing Element number of the whole building model

cavity= ones(length(aElements),1);

n=1;

for j=1:length(aElements)
      
    if combic(j,groupc(j)==1)
    
       cavity(n)=combic(j,1);
       
       n=n+1;
    
    end
   
end

The result "cavity" I get is attached to this question. What I want is the loop to stop, before filling out the rows with "1" and give out a vector that has the length of the number of elements that belong to one part (in this case to the part cavity). How can I do that?

[madhan ravi]

Your question isn't clear, what ones? You already preallocate cavity with ones? Instead of posting a random picture why not illustrate with a short example with the desired result?

cell_array = {[]; 4646; 3883; 0}
desired_result = % ??

[Brendan Görres]

the problem was the preallocation. I missed that.

Answer 1

[Abdolkarim Mohammadi]

The break statement terminates the for loop:

if j > numel(cavity)
    break
end