Creating an adjacency matrix from a cell array

Question

I'm going to create an adjacency matrix from a cell array, but faced two main problems:

I don't know how to access to cell array's elements; so an adhoc method was used.
(and the most important) The code produces an error and the partial result is also a weird one!

The cell array is as the following image:

The code is as follows:

for i=1:N
    L=size(Al{i});
    Len=L(1,2);
    for j=1:Len
        elm=Al{i};
        D=elm(i,j);
        Adjm(i,D)=1;
    end
end

The code produces this error:

and the output is as follows:

P.S.: The code is part of a program to construct adjacency matrix to represent superpixels adjacency within an image. There may be a specific solution for that!

I don't understand... [here](https://stackoverflow.com/a/55085475/7328782) you got code that creates the adjacency matrix. `glcms` in that code is an adjacency matrix. All you need to do is `Adjm = glcms` and you're done. Why do you need to do all of this? — Cris Luengo, Apr 18 '19 at 20:41
Also, "I don't know how to access to cell array's elements; so an adhoc method was used." You are indexing `Al{i}`, that is not an adhoc method, that is the normal and correct method to get the contents of a cell in a cell array. — Cris Luengo, Apr 18 '19 at 20:42
@CrisLuengo, OMG!, I forgot about that . I was looking for a method such as the submitted answer. By the way, thank you for the reminder. — dtr43, Apr 19 '19 at 12:48

score 4 · Accepted Answer · answered Apr 18 '19 at 20:31

There are lots of ways your code could be made better, but the specific error you are seeing is because you want D=elm(1,j); instead of D=elm(i,j);. Note the 1 instead of i.

A somewhat more efficient approach would be to do,

for i=1:numel(Al)
    Adjm(i,Al{i})=1;
end

As with your code, this assumes that there are no empty elements in Al.

Creating an adjacency matrix from a cell array

1 Answers1