help understanding cell and (end+1) use

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gaetano mallardo 2019-3-25

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回答： Rik 2019-3-25

Hi, i have a script where for the first time i meet the cell array. I've read the documentation and it seems quite clear.

The problem is that i don't understand how they set the indices as they use (end+1). To what it refers as i have 2 for cicle?? If the value is end+1= np.max+1, why don't he just write np+1.

Connectivity=cell(1,nnode);
for i=1:nele
    
    idnodei=element(i,:);       
    % number of node for element "i-th"
    np=length(idnodei);             
    
    for j=1:np                       
        nodej=idnodei(j);
        Connectivity{nodej}(end+1)=i;
    end
end

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Answer 1

Rik 2019-3-25

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The end keyword (when used in indexing) is converted to the size of that dimension.

%example:
A=rand(1,2,5,3);
A(1,1,end,1)=2;%end is replaced by size(A,3), so with 5

This also works in other calls:

%example:
A=rand(1,2,5,3);
A(1,min(end,7),2,2)=-1;%here end is replaced by the value 2 **before** the call to min

So in your code end+1 means that you are assigning a value to the next position, which automatically extends the array to fit that size.

NB: I disagree with using i and j as variables here, as well as the lack of any comments whatsoever. You see that a lack of comments causes confusion.